domain reselling / flipping for a living is a very tough game. from what i've seen, the only people that can make a good living doing it deal in the high end expensive names. you'll just be spinning your wheels for a few bucks trying to spin low value domain names.
with domain reselling / flipping, you're only as good as your last sale. and just because you make one good sale one week, that does not mean you're going to make a good sale the next week. you're essentially always hunting and foraging for food.
domain development - actually building an asset that provides recurring "annuity" type revenue is the way to go. if you make $500 in one week on PPC revenue, chances are pretty high that you'll make approximately $500 the next week in PPC revenue - without spinning your wheels cold calling / sending emails / dealing with deadbeat buyers / dealing with deadbeat sellers / etc.
in summary, if you deal in high value names, domain reselling / flipping can work, but otherwise, keep your day job.