I buy anything that meet my basic criteria, in any size (vintage steel road bike, cromoly frame, alloy rims, three piece crankset, priced right). If the bike is my size, it either replaces something already in my "fleet", or it is flipped as well.

+1 I enjoy working on bikes.

My last 8 flips:

1980 Fuji S12S (nice bike, wrong size)
1981 Schwinn Traveler (did not meet my criteria, but I was short of projects)
1984 Schwinn World Sport
1986 Nishiki Prestige (a really nice bike, just not my size)
2002 Trek 4500 (didn't meet my criteria, but it was ready to sell and priced right)
1982 Univega Gran Turismo (thought it was going to be a keeper, but too small)
1992 Peugeot PE-300 (interesting bike! Not my size)
1988 Schwinn Tempo (nice bike, and my size too, hated to see it go)

On the list to go next:

1984 Centurion Mixte (kept it for my wife)
1984 Fuji Touring Series IV (wrong size) (gone)
1988 Miyata 712 (still on the project list)
1983 Trek 520 (may keep it) (gone)