My first bike I got when I was 15 - a friend wanted to buy a new Puch 50cc because the old one was too slow. I got it very cheap, it was an old Goericke, looked absolutely hideous but had a SACHS engine. The nice thing about that engine was that it had a two-gear automatic, which neither a Puch, KTM nor Peugeot or Ciao 50cc had. So I took the cylinder to a mechanic friend who bored the restricted outlet to the header, changed the plug to a hotter one and reassmbled everything. Next day I blasted by the guy with his brand-new Puch Maxi S who didn't know what happened to his old bike.
The first real bike was a CB360, old and used I bought for $200 when I was in California. I never rode it without a nailfile since the ignition points had to be cleaned every 50 miles or so. Once, when I was stranded again, a friend with stopped and asked me: "Why don't you do what the previous owner did?" I didn't see it coming and asked: "Like what?" and he said: "Sell it to some idiot!"
Next was a decent CB450 Nighthawk for $700; sooth three-valve engine, decent power, I did my first trips with it, San Francisco, San Louis Obispo, Highway 101. Great memories!
Then a XS 650, loved the vibrations, 50 horses, cool looks. Had two more much later. Discovered a black one at a repair shop in Honolulu, sitting in a corner, dusty, flat tires. I remembered it and checked it out - it had only 500 original miles on the clock! Asked the owner of the shop about it, he told me the owner brought it in years ago, it had been sitting, didn't start. He cleaned the carb, put a new batterie in, but the owner never came back. I got it for $400, no papers. It cleaned up very well, a '81 model. Lots of chrome polish and elbow grease, new tires and vinyl and it looked like new. Bought an old '81 for $350, parted it out, got my money back, registered the frame and put the stickers on the good bike. Had it for years, put about 5000 miles on it, never a problem. Bit heavy, though.