Someone wants to sell me a moble home. There are back taxes due. Who do I contact to see if it has a clean title? The trailer is in newyork.

Start at the town hall of the town the home is in, and ask for the tax collector or assessor's office, and then the deed office, to see if there are liens on the home. Small towns often have partial hours each office is open in a week. You may have to go in person.
Some homes are classified as trailers, through the DMV, and taxed separately from the land. You will have to determine that after talking with the town hall. They are the most trouble of all, because not seeing a current title in the seller's name means you should NOT BUY IT.
I HOPE you aren't thinking of buying this without seeing it in person, and bringing an expert in home inspection with you to check it and all the facilities (electric, water, sewer) out. And if the home is in a park, that's another can of worms. No matter how inexpensive a home is, either know what you are doing or hire a real estate person for a few hours, in addition to the inspector.