one more vote for dumpster/thrift style. go to every thrift store, etc. by where you live and check out every bike that looks suitable. if it looks like it fits and the frame is in decent condition, and if you like the way it looks, take it home and tear it down. take off the freewheel, screw a cog on the bag, get out your spoke wrench to re-dish the wheel, make sure you have some clips on the pedals, and ride away (carefully). that's basically all there is to it. also, check out sheldon brown's website.