Personally I think you will find that since you need everything else to shave (strop, mug, brush, soap, etc..) the best economic value to start is one of the sets that any of the vendors on this site advertise. Once you factor in the cost of buying the razor from an antique store and sending it out for honing you're going to be near or above the cost of the razor portion of a set depending on how good your flea market/antique store prices are.

All the antique stores I've been to slap $30+ price tags on any razor just because they're old and hard to find now. Even ones with chips, cracks in the blade, etc...

Unless you're in love with the nostalgia of a vintage blade and want to spend to bring it back to shaving glory stick to one of the starter sets IMO.