Unless you want to build a number of wheels, even the minimum investment isn't worth it. My favorite wheel building story is when I was working as a mechanic in the '70s, someone came in and wanted to build a wheel. Which was borderline insane, because our charge to build a wheel was way too low. He said, "I'll be able to figure it out because I'm a mechanical engineering grad student." I told him I was a mechanical engineering undergrad, and that he would be back. Surprisingly, he came back when he couldn't figure it out. In his defense, this was before the availability of wheel building books and the internet.

Even with all the info out there nowadays, people don't really build very good wheels a lot of times. This is true of some people that work in bike shops.