Never ever just leave a deposit with paperwork to be done later. Do the deal all at once. Haggle on the price as long as you need to but once you are ready to sign... go in and either wait for the paperwork to be done, or tell them you will come back and sign, but you are NOT leaving a deposit. Once they have your deposit you are buying that car from them. If they say they must have the deposit AND you have to come back to do the paperwork, something is wrong. Run from that deal.