Personally I wouldn't date a man in his 30s who was frittering money on a professional house share, when he could swallow his pride and spend a couple of years living at his parents house and save nearly a whole years salary for a couple years to get together a deposit. This. I'd be delighted if one of my children did this
Only on mumsnet is spending money on a basic need like shelter described as "frittering away money". And I note both posters who endorsed this are mummies, not the the women who would have to date these man children. Living with other people in a flat share is also a great way to make friends, improve your social skills, broaden your life experience, etc..
OP - I think your DP is not so bad as some, because he has at least lived abroad, but given that he works in finance and has saved a deposit already, I would suspect its a calculated decision on his part to get a woman to buy a property with. So be wary that is what he is looking for and that is part of your role in the relationship.
Personally, I really don't like it. I guess you always have to put him up if he is staying over? And you have no idea how competent he is at cleaning up after himself, paying bills, adult decisions, etc? So its all risk for you and low risk for him. I find it hard to respect a man in his late twenties who doesn't have their own place, never mind one of 34 happy to live with mummy. I'd be thinking if you can be independent, why can't he?