I'm currently UK based and previously went to a US community college and know plenty of other people who have.
Are you currently in the area with the community college he's considering? Many of them have stricter 'in area' fees vs 'out of area' fees - some by city or county for a specific length of time before applying - than US universities which tend to just be by state. The vast majority don't provide or have any on-site accommodations, it's assumed you're local or commuting in from home.
Many states have secondary options programmes that allow high school students to take college classes if they test well enough or need extra provisions, some at a reduced or even paid for by the school district or state, but this varies so much and changes frequently that you'd need to check with the individual high school and community college involved.
If he's planning to go to community college and then onto a US university, it's best that the two are in the same state - many schools have credit transfer agreements and the closer together they are, the more likely that can happen. Those far out of state that will do so from a community college are rarer, often on a case-by-case basis.
The UK doesn't really recognize qualifications from US CC, AAs or otherwise, but they can be used as evidence to get onto UK courses (it's what I did).