I ride yard sale and classified advertisement bicycles exclusively. Best deals so far:
1) $0 for a 1974 Peugeot UO-8, which I rode for several years, until the frame cracked.
2) $0 for a 1973 Schwinn Varsity, which I fixed up slightly and gave away.
3) $10 for a quad-butted CrMo Team Fuji which was too small for me, but I got several good components, including cranks, brakes, and derailleurs, and resold the frameset for $20.
4) $20 for my 1959 Capo, which fits me perfectly (55cm C-T, with a longish top tube).
Keep your eyes open, and get to know your own likes, dislikes, and, of course, size preferences. Never settle for something too large or too small, unless you need components or can trade or resell it to recoup your investment or to do a friend a favor.
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"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069