I built every pair of wheels I ever made on a no-name folding stand I paid like 10 bucks for.
I've also trued many a wheel on the upside down bike... Just tighten the caliper as you go.
Wheels look scarier than they are. Take your time, don't get stressed, accept that you'll screw it up and have to back off and try again. Wheels are fun, maybe my favorite thing to work on.
--Shannon