Eh, he will soon come around. Most young professionals go through this phase. He'll need more support when he moves out and realises how slow and boring normal life is compared to Zone 1

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Regarding "not being able to save", I think he is smart enough to realise that he is simply not yet
prioritising saving for a house. Not being able to save, and
not priortising to save are two very different things.
If he is already on a decent London wage - ~£80k-ish then odds are the sky is the limit for him with regard to earning potential. Like many he is probably thinking that a couple of years having a great time is well worth the delay in the inevitable 'growing up'. Especially if he is a bloke, he can only get more attractive as he matures, gets more dollar, buys nicer clothes and watches and what not.
Good on him for not moving to suburbia and (mentally) dying young.
Edit: The get on the ladder crew are the latest evolution of birds being told to get married and have kids before they're 23. The fact is it'll take software devvy about 12 months to save what most could save in 5 years of trying. If earnings outpace lifestyle, you are double quids in (y)