Maybe he's nice enough to agree to that. But it is the Seller's job to write the Bill of Sale. Some states have a standard Bill of Sale that you *MUST* use. Some even require that both parties have it notarized. So first of all check the laws. Second of all don't think for one second he will accept the bill of sale. I would not sell it to you if you did that to me. In fact someone tried and I told them to take a hike.
Now for the grammar. Once you say "I _____ (buyer)..." You can keep on using just buyer. You don't have to repeat that over & over again.
That Bill of Sale is insane. You are not buying from a dealership. 1st you check out the car. 2nd you agree to a price. 3rd you leave a non-refundable deposit. 4th you drop off the check and pick up the car. You are making this harder than it has to be.
