I disagree with those who categorically say 'don't take the money' - I think those categorical comments are either from those whose parents aren't in a position to help them and basically resent anyone getting help, or those for whom taking a gift like this has gone wrong further down the line - but who fail to recognise that it can be great for lots of people, even if not thes,elves or absolutely everyone.
There is a something to be said for the recommendations of those who say something should be written down about the money being a gift. There can be value in writing down things about where the equity should go in the event of divorce/death, but I'd don't think it is necessary in all cases. Some parents don't gift money like this because they are concerned about divorce issues etc and want to ensure the equity stays with their child. If that is their feeling, and if the young couple receiving the money are happy for it to be given with these terms, then that's okay.
However, I think many who give, give to the family, not just to their immediate child. They give in the expectation that family will stay together and also that if they don't or someone dies, the family will be able to work out how it is shared out - so as they g ie the gift, they hand over the future of that money rather than wanting to lay out terms of what happens next. And I understand that - it really is then 'no strings' giving because if disaster strikes, it will be up to those in the younger family to decide exactly how to use/share out the equity/money, because by then it is THEIR equity/money and not that if the parents or inlaws. So I don't think it would be a failure of planning ahead to not get something written down about future use of the equity necessarily.
I do think the key is that everything has been considered and discussed so there are no misunderstandings. Although such conversations can be a bit awkward, they are important and worth doing when large sums of money are involved. So make sure it has been made clear if it's a gift or loan, and probably make clear if it's for a particular purchase such as a house or if it's a general gift to be used for anything the recipient wants. I'd also check if the gift is specifically for the child if the recipient or the whole family - and as that child, I might just point out to parents giving the gift, that if as child I died, that money would then belong to spouse and later to children - I probably wouldn't be asking if that was okay, as personally I would want to take a gift on the basis it was for us as a family and not just DH, but others might feel differently about that. Personally I wouldn't feel very happy about strings attached to the gift that a house could only be in the name of the givers child rather than both the child and spouse. It would seem a bit like a pre-nuptial agreement if terms are about the money only belonging to child if there was a divorce, although I can see why some parents might want to say that - but I think they'd have to accept if those were the terms, some people might choose to refuse it, because then it isn't becoming totally strings free. This might be fine if a gift is given to a child who is in a new relationship or an unstable one, but where a family has been established, givers of gifts really need to give to that family and accept the family will determine the sharing out in event of a crisis - when you hand the money over, you do hand it over and any responsibility to determine its long term usage is lost, as far as I'm concerned.