But before I go, yes, retirement accounts (especially Roths) are a great place to build wealth and that's where most people have the bulk of their savings anyway. Back when I did JVs with people, they were overwhelmingly using their IRAs, but ya gotsta know the rules. Or prepare to suffer. The issue in what you suggest is that you're not allowed to live in - or benefit in any way from - a house bought by your IRA.
Your up-and-down relatives (parents, grandparents, kids or grandkids, etc.) can't live in it either but weirdly your side-to-side relatives can and that includes your siblings. If you have a self-directed IRA custodian, they will keep you from breaking the rules. If you're going to use a checkbook IRA, you have to know the rules yourself.
Interestingly, my friend with the $100K has been living in the squalor of a duplex (shotgun double) he's renovating into a short term rental so not sure how much zeal he has to do it again, but it's definitely a thought. I will share it with him as something he could do with non-IRA funds. He's also getting historic tax credits on that project so it's turning out to be a profit monster, assuming Airbnb comes back reasonably soon, which we all think it will, right? OK over to direct messaging.