Hey, real funny!!! Wait a minute, you're right...
Imagine my excitement when I saw good ole T-town for someone's location! I don't think anyone anywhere on the forums lives here, I've checked. There's a guy in Perrysburg on the FGG who rides fixed (obviously!).

Bryan, howdy. I'm thinking that the best thing to do, wait, are you looking to build something on your own, or buy built up?

The threads on a freewheel hub are the same as on a fixed hub, the only difference is that the fixed has the smaller reverse threads for a lockring. So, yeah, you can thread on a freewheel for the fixed side, it will engage with the larger threads, and just have the smaller threads hanging out underneath, if that makes any sense.

Welcome to the forums! As a warning, it gets kinda nuts around here.