Some clubs are sneaky expensive so that's a good niche. I've found some gems before in stores and on the curbs. The only catch is that shipping can be a little expensive. All it takes is one good putter or driver and the digging through the crap is worth it.
RE: DIY Income From Thrift Store Flips -- $65 Spent Turned Into $1,443 Sales Revenue (22x Return) -- Buy Low, Sell High!