Sorry, are you saying your children are all out of education and are not working and you’re supporting them as well?
Im all for helping children get on their feet but are they even looking for work?
Do you think that this might be part of the reason he thinks you are easily manipulated?
In a way OP, I don’t want to focus on the money (others have done that really well). I’m more concerned that you feel guilty about considering your own needs and wants. Have you been brought up to believe you should put everyone else first?
Another adult should not be telling you what is happening with regard to life changing decisions: I’m moving in; I’m paying x in rent. The conversation should be: I’d really like us to live together, as we’re at that stage in our relationship. Is it okay for me to move into your house?Let’s have a conversation about how much it’s fair for me to contribute, so that it’s a good deal for both of us and because it will cost you more in food, water (if you’re on a metre) household items like shower gel, washing tablets, electricity (for his washing, for appliances on when you’re out) etc.
It’s fair that you BENEFIT from the arrangement as much as he does but certainly that you’re not out of pocket!
No one should be telling you how things are going to be. A grown up decision should be a negotiation, with both sides having a say.
Also it sounds like your children aren’t really children any more and that they should be contributing too.