[diegomcfly]

>I am in a professional job, and I doubt I could afford a decent place to live without parental help other than a crappy flat in a dodgy area.

Then live in a the "crappy flat in a dodgy area".

>How people afford to live by themselves, on non-professional jobs I don't know.

Then don't live by yourself. I had 2 and 3 roommates over various times as a young person getting started. We split the rent in crappy small apartments.