He will be entirely dictated by his budget rather than where he wants to live at the prices.
Suggest he gets on spare room and filters by price and starts Messaging people.
I’d look east on the DLR and central line. He’s a young lad, he might prefer lower quality accommodation over location. Shadwell, limehouse, mike end, Stepney, Stratford and Leyton. Probably no further than Leyton.
Central line is busy but they come every minute orettt much in rush hour and it’s only 4 stops from Leyton to Bank.
Or also north east along east London overground haggerston and dalston.
Plenty of shared flats in ex-LA accommodation in the places I’ve mentioned. Leyton it’s more house with yard/garden.
Hackney Wick is very cool if he likes raving, lots of club nights are morning there.
It’s much nicer to get a room in a shared house that has a sitting room. Most of the crappy ones turn it into an extra bedroom. A shared social space is much better for making it a nice house and social experience.