Well, you got me dead to rights.
What started me out was the JaParamount I found in the trash. I sold it because it was too small for me, but not before I built it back up with a full Shimano 600 STI group, right down to the hubs, and period-correct Mavic SUP rims. I got $350 for it, which was a good price considering its condition and equipment.
I also have sold 3 Nishikis: a Sport, a Riviera GT and a Modulus (converted to all Shimano 105 STI), a GT ZR5000 (full RX100 STI,) a Schwinn LeTour (Exage,) a damn near 50lb Peugot, a Motobecane Jury, and a Centurion step-thru from the 70s. Seems like there was another I forget, but I think that's it.
I sold them all in not fully restored, but reworked condition. All of them needed something and left me looking good and riding like they should, not with silly colored tires or deep-Vs, not just with new bar tape and tubes, but quality vintage period-correct parts. All of the money I "made" went into my next build, and not one single person has come back to complain about any of them. I would know it because my email and phone number haven't changed since I started flipping. I'd buy any and all of them back, and I let my buyers know it, too.
My problems with most flippers these days: People that turn decent quality road bikes into fixies really chap my ass (like the guy who bought my Riviera GT,) especially considering all the options for track fork end frames out there (I built up my current Nishiki into a single only because it has no shifter bosses or derailleur hanger on the stamped drops.) Also, people who sell nearly ten year old Tiagra and Sora equipped bikes at near MSRP when I can get a 105 or Ultegra equipped bike for the same price, as well as someone who would sell an old Schwinn Varsity for the same price as a late 80's World that weighs half as much and has better components. That's my three cents.