Unlike the others I think the basic premise is sound. Yes it does have a twinge of entitlement to it, but compared to what I’m seeing in the world today, hell you should nominate yourself for sainthood.
The major risks are them needing most or all of the money before they die, a not insignificant risk. Of course if you buy at or near the bottom of the market, its not a problem because its all up from there! The problem is knowing you’ve reached it and being able to solidly convince yourself and your folks that its so.
Finally what you are talking about is an inter generational loan. They always come with strings attached. I know my father was going to loan me 25k to buy a house. When he found out I was going to buy a motor cycle he told me he wouldn’t help me buy the house if I did. Better know what those strings are, they can be more damaging than owing money.
Finally, weren’t you the guy who convinced himself a year ago to buy a new tract home in Temecula? (7th circle of hell) If so do you really think you are in a place to call market bottoms?