When you leave the country you buy a ticket. when you come back home do you have to buy a new ticket?

Question

do you have to buy another ticket or what?

Answer 1

If you're talking about an airline ticket:  Most people just buy a roundtrip ticket before they leave.  You could still do it the way you said, but it would probably be more expensive, and buying a one-way international ticket is a good way to get more attention from security officers.