Would agree with the other responses that money and family can be problematic and that the title is a bit different than what you describe - financing the house for you. Unless you just cannot qualify for a mortgage, I wouldn't even consider that circumstance. And if you cannot qualify, lenders are pretty lax really and money is cheap, you should probably work to get in the position that you can before taking on that burden. If he was truly buying you a house and giving it to you with no strings, I don't know, maybe. To me a lot would depend on his personality and you and your wife's personalities and relationship. The fact you consider the possibility she would wake up mad at you and leave is not a positive.
My wife and I are in the camp that we would like to help our kids with down payments on a first home purchases when that time comes. But it would be a pure gift with no strings attached. Maybe it would be better to just use that money for nice extended family vacations regularly. Thankfully that decision doesn't have to be made yet for us.
We have learned the hard way. About 12 years ago we purchased a small house for my MiL to live in. The initial understanding was that she would pay a reasonable amount every month in rent and we thought it would be easier than having to move her around from rental to rental constantly when we are out of state from her. She paid "rent" for a couple of years. Then without a word or discussion or apology, she just stopped working and stopped paying. So we pay the mortgage and the utilities. The relationship between her and my wife was never awesome, but now it is really pretty bad. But it is kind of an elephant in the room type bad, not a topic that gets discussed - just an external stress and it definitely affects how much we visit. Honestly, to us, it is less about that actual money than about the fact she did not ever discuss it with us or say she was sorry or thank you for helping - just stopped paying. I don't think we really thought it would not go the way it has gone, but it is still a bit frustrating. I eventually thought through it enough that I am at peace with it. I wouldn't be okay with kicking her out, I knew it was likely going to turn out this way when we signed up, it is what it is and I try to think of it as a gift to her and hope karma will work out for us on it in the long run. If nothing else I take solace in the fact that we would have probably had to help financially either way and at least this way we have an appreciating asset and we don't feel too bad letting my wife's siblings, who live in the same city, bear the burden of day to day help and interaction.