Thanks for your thoughtful response. I may go for that trade-in deal, or buy another cheap printer (just for such a deal) if I get this one working. At worst I have a really good $10 scanner. I will see if Cartridge World will let me try a color cartridge. They are more concerned about the ink than the seal on the package. Not gonna stick my neck out again on this printer!
She (the seller) seemed to have a good talking point. She was using it for her small business (right there) and needed to replace it fast. People can't hardly give these things away! I have already passed up a few free ones because I didn't have the storage space. Her sister was married to the manager at Office Max, so she could get new printers at cost. I also bought a $6 non-working Officejet 7130 from her because my 7130 has a burned out carriage parking motor. She priced it at what OM would give her for the empty cartridges.
I have been burned before on electronics, so now I only consider things that are priced at or below salvage value, or working while I'm there. If not I make an insanely low offer. For example, I recently bought a 2GHz HP dual-trace oscilloscope with all the probes for $10. Just the probes are worth over $100 used, if you can find them. I got him to put it through the paces while I was there. In the last hour of the third sale day people are ready to deal when you give them their very first offer.