How much would a standard ultralight cost in terms of both purchase
(or building) and operating?

What about a 2-place one? Yes, I know they are technically not
ultralights, but I'd get it registered as an airplane.

I ask because I'm going to build an airplane of some kind a few years
from now, but I don't know how much of one I'll be able to afford. My
ideal would be an RV-7, but that'll probably be out of my price range
just out of college.