In NY, is it legal for a used car dealer to advertise a "cash price" and eventually charge a higher negotiated finance price?
If you agree to the price of the vehicle when financed, then it would be permissible. However, the difference between the higher price and the cash price could possibly be considered a "finance charge" and would have to be calculated into the "A.P.R." That is, the cost of the credit would have to include the additional amount you are paying above the cash price.
Please contact my office directly if you would like to discuss your situation further.