I'm a roadie looking to convert a BMX to a fixed wheel. I'm new to building so any advise would be great. I can't seem to find any BMX rear wheels that come with a fixed hub. Am I going to have to buy a seperate hub and have it spoked to a 20" rim? Is there anyway around that (thats safe)? Also, my fork is loose (what can you expect for $20 on craigslist). Again I'd appreciate any advise.

Is the bearing race on the fork "wobbly"? And yes, you will probably need to get a separate hub.

What's a "bearing race?"

Oh sorry...it's the ring above where the forks' legs meet the steerer. It looks like part of the fork, but it's not. You have to take the forks out to see it.

Why do you want a FG BMX bike?

get a coaster wheel and weld the hub to the gear.

I am going to have that done to my Redline Pro Cruiser with a flip flop hub-freewheel. The shop is charging 140$ including building the wheel. For rough streets it should work just fine and be a lot of fun.