trust your instincts.
not saying he is a bad person, or up to anything, or a conman, but the majority of men are not; that's not a reason to live with them, or rather have them living with you in your territory.
if he'd had his own place when you met, you probably would not have moved in together.
this all seems rushed. his flat purchase fell through, and you appeared on the horizon, with a nice, well-run house and open to hooking up. it was v convenient. I think you both enjoyed a change, someone to be romantic with, but...
I doubt that it has legs. it will not run and run. and your doubts, annoyances, and resentment will grow.
i'd say beware. he is not fully committed to you, rather enjoying a kind of friend with benefits and board/lodging.