I think you'll be able to get a lot of decent stuff for that amount of money.
As a boy who's "just starting out", I think a modelling amp is the way to go. It will not only give him a decent sounding amp, but also a lot of different amp models to choose from within the same amp. Not to mention a lot of nice effects, which are quite expensive to buy seperately. When his ear becomes more conscious about sound quality, he can upgrade to a more expensive tube amp or something.
So what to buy? The best thing to do is to go to a dealer with a good selection and try the stuff. Sound is of course first priority, but it's difficult to measure objectively as taste differs from person to person. Portability is also important. I guess he'll be lugging it around a bit, so it shouldn't be too heavy. It should be fairly simple to use. Some amps have hundreds of (and many useless) sounds that are tricky to access because of clumsy menu systems, so it's better to have a few great sounds that are easily accessible than hundreds that you have dig deep into a data bank to get at. It's possible to get amps that combine digital modelling and tubes, but tubes need to be changed every so often and must be handled with more care, so I recommend avoiding that for now.
From what I've read on forums and seen on YT, it seems a Fender Mustang III is a good option. It should by loud it enough too. Maybe a bit heavy (16kg), but loudness unfortunately often implies heavyness. BUT - go and test the stuff