I was always helping my buddies out with their vintage bikes, and we would buy a junker, strip it and leave all the unwanted parts in my shed. Pretty soon I had amassed quite a collection, which led to some interesting frankenbikes, but about a year ago I went back to school, so to earn some money in the evenings I started cataloging all of the leftover parts, and selling them on ebay. Now I look for old rusted hulks, and I am not picky, I would grab a kz400 in a second if just for the carbs. Carbs, tank, seat, plastics, igniters, coils, wheels, radiators, cables, airboxes, carb boots, calipers, master cyls, headlights, gauges, heads, camshafts, cranks, headbolts, starters, titled frames, all are worthy items to sell on ebay, and fetch quite a lot. At the moment, I make about $600 a month on bike part outs, and I lay hands on about 1 bike per month.
Some people look down on the practice. For example, I just got a vulcan with a seized engine and no title. I tore it apart, and posted on the vulcan forum offering parts. Those guys responded telling other people not to buy form me because I was an opportunist and not a member. The way I saw it, I was offering these parts to them, allowing them to name their own prices (within reason), and saving these totally decent parts form rusting into the ground or getting junked. I mean, eking some kind of utility out of trash is one of the basic tenets of sustainable recycling, and I'm not saying that I am Al Gore or anything, but I don't see how it is not a win-win-win-win for everybody if the original owner gets some cash, I make a little bit of money, the postal service is helped form going bankrupt, and motorcycle owners get the parts they need.
Ebay can be a pain. It seems like they are always raising their rates, and yeah there are those impossible to please sellers. A lot of people read "as-is" and assume "perfect restored condition," and are surprised when the part they receive is not up to their expectations. The majority of the power is in the hands of the buyer, and the appeals process is biased heavily towards the buyer. But you do your best, move on, and work it out.
Times is tough man, you gotta hustle what you can. Parting out bikes has taught me a lot about mechanics, its really fun to play in the sun with machines all day, and the money isn't great, but its nothing to scoff at either. $600 covers our rent, and I earn that in the afternoon it takes me to strip down a bike, the rest of my time is spent in the AC in my underwear, posting ads.
I say do it if you can. There are TONS of bikes out there, and everybody knows somebody with a rusted old hulk in their backyard.