How can I sell a property that has unpaid back taxes?

What sort of a dimwit would consult a realtor for legal advice? Realtors do not need any higher education whatsoever in order to be a realtor and they cannot give legal advice.  You should have consulted a lawyer.  Obviously, you didn't know how to search the title, because taxes do not suddenly show up months down the road.  You missed it, through careless viewing or whatever, you failed to properly look at what what there.  The seller can "say" anything he wants to but if you buy a house with taxes owing, then the taxes become your debt.  You can try to sell it with the taxes outstanding but, most people will offer that much less, figuring on paying your tax debt.  Some people will just walk away because it represents a red flag - no money to pay the taxes - no money to properly maintain the house.  They will wonder what else is wrong with the house.  If you want top dollar, pay the taxes.  You can sue the seller if you want.  Who is to say - you might be very convincing, but it would be much better if you have the seller's declaration in writing that he will pay his outstanding taxes.

realtor is not expert on this....to sell it, you need to make enough profit to pay off the taxes....