This is a good idea if you can find a reputable service that will guarantee your money back.
I bought a used Note 3 off of ebay. I got it, popped my SIM card in and worked perfectly. Then one day I couldn't make calls, use data or register at all on the network. Turned out it was on a carrier payment plan and the original owner stopped making payments. So T-Mobile blocked/blacklisted the IMEI number. T-Mobile refused to talk to me about it or even let me pay it off. I sold it on ebay for about $350 - afterwards I realized that for $50 I could have had it "fixed".
And I'm sure I'm not the only one that has been scammed like this. The sad part is that it only scares people away from wanting to do business with honest people like me because of all the idiots out there.
>" If you were to buy a device on Swappa that could not be activated due to a blacklisted ESN then you would be entitled to a refund no matter the seller's stated return policy."
They don't allow selling blocked or less than good condition phones at all. You can usually get your money back from ebay from a deal like that if you fuck with ebay support for long enought though.