Used legion Go's???? What should I look for?

My son who is 10 has been hassling me for a gaming PC....however its a big cost, and it takes a large amount of space which I dont really have, and I fear his 2 little borthers wont be able to keep their hands off it. So I was thinking about getting a Legion Go. I think this would suit him well as he can take it with him when he wants space, but also should have enough functionality for him

I've had a look online on places like Gumtree and Facebook marketplace and have seen some for around £350 to £500. I was just curious firstly on peoples opinions on whether this would be a good option/alternative to a full gaming desktop, and also if anyone can advise what I should look for when buying one?

Thanks.