I just got into flipping this year after rebuilding my own bike and finding out I really enjoy doing it and (I think) I'm pretty good at it.
I don't always do a complete disassembly but everything gets cleaned, greased and anything requiring replacement gets replaced, I won't sell a bike that's not 100% functional and rideable. If the bike is nice enough to justify a bare frame tear down I do it, it's not like it's all that hard to do.
I think I sold about 15 bikes this year and I've got about a dozen or so in line right now, I'm currently finishing a nice old tall frame blue Uo8 and I'll be tearing into a white Uo8 right after that.
I've found that I really enjoy working on road bikes, couldn't care less about mountain bikes and I don't know anything about three speeds so I stay away.
Just keep watching Craigslist, One thing to try is to just search bikes by brand from the main page because a lot of garage salers just mention the bike in their garage sale add and don't post it in the bike section, I found a gorgeous little 1984 Peugeot that way and picked it up for $30.00.