If he just wants to play games a console is a better bet, they work, require no effort and you’ll get a decent amount of years from one before they’re obsolete.
If he’s determined to play it on PC but shows no interest in messing with stuff or building it up you can do it cheaper and easier buy an off the shelf PC from a decent brand (i5 processor ideally, older 4th Gen are cheap now) and a entry level GPU – Novatech have a SFF GTX750Ti for £80 or so, it doesn’t need its own power input etc and will run even the most current big games reasonably well. You can add more RAM or an SSD later on which will make it quicker and he’ll learn a bit about IT, home gaming like as a teenager is how most of our techies in work got started.
But if they want to be a ‘real’ PC gamer and spend their evenings worrying about FPS rates tinkering with software and hardware more than they spend actually playing buy a case, a motherboard etc and build it together. If you can build a bike you’ll piss a PC, same sort of compatibility issues, but if you get it wrong it just beeps instead of working instead of the bars coming off at 20mph.