Learning to drive might increase your earning potential, OP, so that should be a priority.
Is (was) he thinking of buying a brand new bike? I think that's bonkers, it will lose shedloads in depreciation in its first year. Bikes are expensive to run. They seem to need tyres, brakes etc more often than cars. Tax is generally low, but insurance may not be, especially if he fancies something fast.
As well as the bike, he will need a crash helmet (min £200 for a decent one, and cheap ones are ill-fitting, uncomfortable, noisy and probably less safe) decent boots (min £100, although DPs were £280 - birthday present from me), good waterproof jacket and trousers, with protection for elbows, shoulders, back etc (£200 and £100 min respectively, cheap ones will stop being waterproof after one winter), gloves (two pairs, one for winter and one for summer, both with CE standard protection), full thermal underwear for the winter months, and, ideally, I'd recommend a pair of neoprene socks, too. This isn't being extravagant (extravagant is Rukka bike gear, about £1,500 for trousers and jacket), but the minimum for keeping dry and safe.
I wouldn't fret too much about the danger if he's a sensible driver who is good at anticipating the behaviour of other drivers. DP has been riding bikes for over 40 years and hasn't had an accident for 37 of them (and that one wasn't his fault!). That includes 15 years of working full-time as a motor cycle courier in London, doing several hundred miles a week.Accidents aren't inevitable, and the people prone to them tend to give up biking after a while, because they don't like falling off.
But he should save up and buy secondhand initially imo.