Dp's son is 23. He has done extremely well and picked up a great job starting in a few months time. He has previously been renting with friends.
We have a bit of a chequered history - a few years ago he stayed in my house and caused a large amount of damage (£2,000) when he had a party. He lied about it and never owned up to it or volunteered to help pay for it. For a year I refused to let him stay in the house by himself and then in lockdown, when dp and I went to stay overnight to do caring duties for his mum, he told Dp he was really struggling mentally and needed a break and was right round the corner from the house and stayed there for a night and hooked up with random men off the Internet and had them round the house for another party. The neighbours saw it and called us and he eventually admitted to it.
This is my house he is doing it in btw not dp's - not that it matters but dp moved in with me when his son was 19 and already at university so this house has never been his permanent home.
I think he is a chancer and always will be. He has told dp that he wants to stay with us so he can save some money. His son's job will pay more than dp is earning. I have to keep a bedroom for my SN son who is away but still has his home with us (he's 19 but will always need support and comes back regularly), then dp's 2 other dc visit us every other weekend and the other bedroom belongs to my daughter (20) who is at university.
I've told dp that if he was to stay with us, I would still expect him to contribute financially and more importantly, I don't know which room he would take. Dp is now suggesting he could stay in dd's bedroom.
I just don't think this is practical (what do we do when dd comes back!) but also I really don't think it's going to work. He has already shown he has no respect for me by abusing my kindness in letting him have the house to himself twice. If he was under 18, I would absolutely give him another chance but he isn't.
But am I am being too harsh? I would never want to think a child of mine didn't have a home - but on his salary he could easily rent again with friends (as he does now) or find a house share.