In home care has a high value and huge commitment, specially if you live a long life. I would call it an equal trade; house for care commitment.

If outside aids are needed, the cost could well exceed the value of the real estate. If adult child is the caretaker (not clear from the post) he or she will earn the house through caregiving. It is exhausting, 24 hour per day work. If adult child is paying for aids with his/her own funds, the cost could well exceed a typical mortgage payment.

place to send their kids.

which we purchase and share a couple of time per week. We are primarily looking for a guaranteed place to stay until assisted living ,undertaker or whatever.

We share social time.

He’d help the others as they needed it. Never thought about what was equal.

My in-laws had a family cottage. The sold it to two siblings at the assessed value.

Two decades later when parents died the assessed value was taken from inheritance.

I guess not all families have a final inheritance. But the siblings who had the cottage have way more value than the monetary inheritance.

It’s all good with us.

The first one that leaps out is whether there would be a commitment on the part of the sibling who buys the house to take care of you in old age, and to what level of care? Would they be committing that they would never sell the house as long as you live?

We interact socially.... meals and so forth. They are interested in the local elementary school (good ratings) and we all like the neighborhood.

We do not want care beyond looking in once or twice a day to make sure we are still alive.

After the final value is figured, 1/4 to each of the other three.

Make a provision/arrangements in case the house has to be sold while you still need care.

Someone will always think it was not 'fair', so do the best you can.