Enabling Children

We did this approximately by accident.  We had a kid, and separately had a habit of letting our friends crash in our spare bedrooms, and one of them did enough caretaking (letting us SLEEP!) that we were like "wait... if she leaves... that will hit the kid like a divorce" and arranged to keep her forever.  Now we live with her and her fiancée and additional Spare Room Friends and a second kid, and we are very crowded in our large house and don't have room for any more Spare Room Friends which is very sad, and plot to purchase neighboring houses as soon as they come on the market and knock down intervening fencing.

We really like this arrangement and so do the kids, and it's been especially wonderful during lockdown since we can do well-attended in-bubble dinners and D&D and TV nights.  It might be hard to do on purpose, especially if you want to do it before you actually have a kid for people to get attached to.  Finding one compatible coparent who is committed to being in it for the duration of at least one childhood no matter what kind of kid you wind up with is already pretty hard.  But we know a family who invited in a Spare Room Friend expressly on the expectation that the SRF would help take care of their child, which seems pretty doable, and if things didn't work out they could presumably swap for a different SRF.

So I guess my advice is acquire at least one spare room and invite a friend who likes kids to live in it and see if they and your baby get along.

It seems like this is a single building version of a gated community / suburb? In "idealized" America (where by idealized I mean somewhat affluent, morally homogeneous within the neighborhood, reasonably safe, etc), all the stuff you're describing already happens. Transportation for kids is provided by carpools or by the school, kids wander from house to house for meals and play, etc. Families get referrals for help (housekeeping, etc) from other families, or because there are a limited number of service providers in the area. In general, these aren't the hard things about having kids. 

In my experience, here are the hard things:

• The early months / years are miserable. The kid wakes you up in the middle of the night and won't go back to sleep and you don't know why. You're in a constant state of sleep deprivation. This happened to me even though I had a night nanny for the first few months (which was hugely helpful, but did not completely eliminate the problem). I got off easier than my friends who had such a problem that they finally hired a "sleep coach" (yes this is a thing).
• Your kid is sick, and you need to take care of them. You could outsource this if you had live-in help, but in practice there is a biological imperative to make you want to do the caretaking yourself.
• Your kid has physical or mental issues. This doesn't necessarily mean anything like they're in a wheelchair or have severe learning disabilities, it could mean something like attention issues or delayed fine motor skills.
• The kid needs almost constant supervision, particularly in the early years. Again you can outsource this to a limited extent (e.g., with daycare) but as a parent you want to spend some time with them (because if not, why have the kid at all?)
• Even when things are going smoothly, there are significant coordination costs. Do you and your partner both need to stay late at work? Figure out who's going to pick up the child from school (and make sure the school has all the appropriate forms allowing that person to pick up), arrange childcare for the night (will you be home early enough to put your kid to bed?), etc.
• You finally got home and you're dead tired. Unfortunately at 3am your kid wakes you up because they had a bad dream. This happens more than once per week, for various reasons. 
• There's a trade-off between living in the best place for your work and living in the best place for your kid. Would it be better for you to live in the heart of Manhattan (or wherever) for your job and career socializing? Probably yes. Is it the best place to raise kids? Probably no. 
• You can never again give 110%. You know those couple of weeks you had crunch period and had to work 80 hours? You can't do that anymore. No one else can actually replace you as a parent for your own kid. Or rather you can, but you have to be aware that you're now actively putting on the trade of "sell relationship with child." 

Sure, I’m interested. But like you pointed out it’s pretty difficult to pull off. One of the biggest consideration is finding the right people.

I think ThomasJ makes a good point that it might be easier to find the right “neighborhood” that already has the right kind of people.

We've done some amount of this, as you reference. I would strongly enjoy having more children around, and I think my kids would like that a lot. On the other hand, there are drawbacks:

• Parenting styles very enormously. It's very hard to watch someone else's kid if you disagree about how to do it. I think this is much less of an issue in extended families, and especially historically, because there's better agreement on how to do it, but I know a lot of people in houses with multiple adults who have a lot of conflict over this. How closely do you supervise the kids? If one of them is hitting the other do you do something about it or let them sort it out themselves? Can they eat whenever they want? Can they have candy whenever they want? How messy an activity are they allowed to do on their own? If they do something wrong what sort of discipline do you use?

Kids are very good at understanding that different adults have different rules, and if sometimes kids are being watched by a parent and other times a nanny this isn't a problem. On the other hand, when multiple adults are present at once it's not clear which rules to apply, so you need more communication among the adults to have a consistent system. Otherwise the kids are going to spend all their time jurisdiction shopping and poking at edge cases.

• Kids are messy and noisy, and different adults handle this differently. I'm also not very confident in adults ability to predict how their preferences will change after having kids. Perhaps your cleanest roommate will turn out to be exhausted and overwhelmed by child care and decide that keeping things tidy is just not a priority. This combines with the previous point: some parents are going to be okay just letting the kids yell, while others aren't.

• I'm pretty pessimistic about strategies that involve building a new intentional community in a rural area, because you're putting all your eggs in one basket. In Boston I have many communities, and while I'm close to my housemates they're not that my whole world. If something happened where we stopped getting along, we all have other options that don't totally disrupt our lives. The rural approach is definitely cheaper, and going into it with several other families does cover some of the normal downsides of isolation, but I'd expect this to be much higher variance than I personally would be comfortable with.

Generally, strategically living with other people (having your friends live next door, rather than strangers next door and friends in other parts of town) seems like something that could tremendously increase quality of life, but is difficult to organize. Kids just add another level of complexity to this problem.

The added complexity of living with kids is that you also need good schools nearby (unless your plan is to homeschool), and playgrounds. But more importantly, the place with kids needs to be larger than the place without kids. So for example, if you would already have a nice rationalist block of flats, with flats large enough for a pair of adults, they would not be large enough for a pair of adults with kids. So you either need to move after the kids are born, or you need to live in an unnecessarily large place before the kids are born. (Buying an unnecessarily large place, and then renting the extra rooms while you don't have the kids, is a possible way to do it.)

If you are a millionaire who dreams about having a rationalist community house, you could probably pay someone to build a house according to your specification -- you wouldn't need to wait until one spontaneously appears on the market. There are already companies that build houses, they would probably be happy to have a guaranteed buyer; you might even get a discount. Though it might be difficult/expensive to find a place to build in a good location.

The problem of people needing different amount of place in different stages of life, could be solved by having places of different size in the house, so that you move to a different place when your kids are born, and move again when they leave home. Alternatively, some larger places could be shared by more couples without kids.

It would probably be good to have a silent "work/study room" where people could temporarily go with their computer to avoid all noise. And on the opposite side of house, a shared "playground". Maybe also a "gym"; and some common room for talking / dancing / drinking, i.e. noisy activities for adolescents and grownups.

In my opinion, unless there are conflicts with neighbors, living with people you know is always better than living alone among strangers. To prevent conflicts, as they say: good fences make good neighbors. Every family should have their private place, where they make the ultimate decisions. Plus, there can be communal spaces. Living close to each other, but with the ability to close the door and leave everyone else outside, when you need it.

Kids aged 0 to 2 need to be with their parents almost constantly. But even then, friends living near can help with all other activities, such as shopping, cooking... or just being there and talking to you, to prevent you from going crazy.

After 3, kids can play together. An adult should supervise them, but the ratio of adults to kids improves dramatically. (In many aspects, having two kids is easier than having one. Two kids aged 3+ will play together a lot. One child will constantly seek your attention.) In a playground or a community garden, one adult is enough to supervise a group of children; especially if there is an option to call a parent in case of problem. Going anywhere else, there is the problem with safely crossing the street; plus the risk that multiple kids will simultaneously throw a tantrum, or decide to run away in opposite directions... so it's like 90% of time it is okay, but you want to have some help for the remaining 10%. Essentially, you can have a small informal kindergarten.

No experience with older kids, yet.

Ambitious people do cooperate to raise their kids. They hire babysitters, in-home tutors and teachers, and send kids to camp. They also send their kids to each others' houses when convenient for parties and hangouts.

If people choose not to have kids because they're ambitious, it's for any of three reasons.

1. They straightforwardly prefer their career to childrearing, even though both have value, and are in the process of wrapping their head around the opportunity cost of choosing not to be a parent.
2. Being too absent as a parent is socially and legally sanctioned. For example, it's not OK to say "I want to have a kid, get divorced, and see my child for a few hours every other weekend, so that I can keep focusing on my career! That's the perfect amount of parenting for me!" And yet this outcome happens often enough that you have to wonder if this is the conscious goal for a fair number of ambitious people who are driving their marriages toward divorce.
3. Parenting is too expensive, or cheaper/more intensive babysitting arrangements are too complicated or constraining to arrange. It's not considered responsible to say "I'm going to rack up a bunch of debt paying for childcare while I'm still in school, but it doesn't matter because I expect to make plenty of money to pay it back later on." Even though it might be OK to take this strategy sometimes. Imagine, for example, a med school student who knows it costs around $10,000 a year to pay for childcare. They pick a $200,000 medical school rather than a $250,000 school, and use the savings to fund the first 5 years of raising their child. Likewise, you could set up a gated community with a bunch of other parents. But what if 50% of the families move out over the course of 5 years, and a bunch of strangers move in with you having no control over who they are?

I'd potentially be interested in doing something like this in Boston -- the main constraint for me would be finding the right people. Gotta be friends with both me+my wife, not just me.

Is this substantially different from "cohousing"?

There are a huge number of existing projects like this, with a huge variation in the degree of "codependence" from one community to another. https://www.cohousing.org/directory/wpbdp_category/comm/

I'd be baffled if there was no matching site for young parents on the Internet.

I am too lazy to google this but if you have 30 mins, I'd love to get the results of your investigation;)

I think most parents are doing a variation of this, although not actually co-living with other families.  By the age of 5 most parents farm out education, food preparation, etc.  Basically the only thing the parent has to provide on their own is parental attention.  This too can be passed-off to extended family, which is maybe the most straightforward option for anyone interested in a co-living situation.

Overall, I think the co-living situation has a lot of benefit in terms of social development for all involved. Western society places a large emphasis on the individual, but many people are lonely as a result of this.  Co-living with others, whether it be like-minded people or multiple generations of a family, is a huge potential antidote to this, and would likely result in more well-adjusted children.

I think the real problem for ambitious people is that they can't turn their ambition off.  Meaning, while they are ambitious in the pursuit of their own goals, having their own kids often means that they become ambitious about their kids' education, sports, etc.  We saw this with the college admissions cheating scandal, which was essentially a bunch of ambitious parents pushing their own ambitions on their kids.