Er I live in the UK and my daughter's room was divided by bed sheets.
We had 4 kids and could only afford a two bedroom apartment. We were not allowed to make structural changes to the property.
accommodation in Europe is very small compared to the US. Especially in the inner cities.

We lived like that for nearly 8 years before another property finally became available. My eldest was17/18 at the time.
So it's totally feasible, however it strengthens even more my feelings that there is more to this than simple attraction.
The age thing? I dunno, everyone is different, but it also means he has virtually nothing to offer as a possible citizen. Providing he is being truthful about that.

What are his plans?
Where will he stay, he can't work, so how will he provide for himself.
What does he do for a living.
How much does he earn?
Where did he study?
What are his family like?
Is he religious, if so what's his orientation?
What does he want for the future, and how will he achieve this.?
Has he ex girlfriends back home with children? If so how will he support them whilst here.?
Are his parents well or are the ill and likely to need support in the future.?
Why does he want move to your specific area of the US.
What are his thoughts on family, does he want kids, if so, how many.?

These are all good things to discuss and sort out ahead of time because unlike a normal relationship it's much harder to just back out of.
If your to make plans make them solid and practical.

I might point out, that even after a year, me and my partner don't live together. At the end of the day I can tell him to go home. (Thank God. )

Take care.