Thanks for your thoughtful response. So he does contribute to household stuff but in a relatively haphazard way I.e. he pays for some of the bills regularly but any more than that is just as and when his mum asks for it, there's not formalised rent. And considering how much disposable he has, I don't think it's very much.
When I said I think he really needs to think about moving out as his family dynamic isn't great (as I say, there's a bit of a weird living off each other cycle going on) he said he'd start saving $1000 a month to build up a buffer. I both thought this revealed an immaturity in that no one goes from instant gratification spending in the moment to saver of the year overnight, plus indicates approximately how much he's getting through monthly on nothing.
He spends on eating out a lot, never taking packed food to work. Random treats. Covering his brother for things. Basically loads of small things you'd buy if money was no object.
He's invested in a couple of hobbies which is fair enough but I think even with that expenditure, there shouldn't be nothing.
It just seems like he's an instant gratification person who is so in the present he hasn't looked to stretch himself any further than his current, not great dynamic, situation.
It's very at odds with how empathetic and professional he is in other spheres of life.
I think I struggle with these things because I'm so happy to be independent that I have had people point the avoidant attachment "you're the problem" finger at me. And I do definitely pull away and find consistent deep closeness a challenge (though I don't do any game playing and weighing up other people that apparently avoidants do??). I do want companionship but I think because my attachment isn't perfect, I find navigating the "are they really bad news for me vs. Am I just impatient and pulling away" very difficult!!
Rambling non-answer but that's my honest thoughts!