And then when it comes time for the first payment, pay it down to a small amount and then divide the rest into small payments he can make over 36, 48, or 60 months.
The 2 benefits to doing it this way is that you will save a bunch in interest and he will also have the benefit of having a larger loan on his credit history than he would have if he financed the smaller amount to begin with. Then when it’s time for the next car purchase which will inevitably be more expensive, it’ll be an easier “step up” in loan amount when a loan officer is looking at his auto loan history.
*source: me. I worked in the finance office at a dealership for almost 10 years.