If he/she is working and can afford it yes.
No a 16 year old cannot buy a house even he/she is financially capable of it.
No, you see many child actors own property. BUT you have to be 18 to get a mortgage on the house.
No. You are too young to be thinking about "boyfriends" and "girlfriends". Just be a friend with him and maybe someday he will be more.
If they can swing the financing or pay the cash there is nothing preventing an 18 year old from buying a house.