Has anyone heard of the startup, Wrapify? They have a service that will provide free ad wrapping installation for your vehicle and can earn you money while you log the driven miles by tracking with your phone app.
They claim people make anywhere from $400-600 per month, and I've seen some posts online of people reporting .60 per mile payouts. The only caveat is that they will not accept your car if it is too old and not good looking enough (older used cars are a fan favorite in Mustache land).
I recently bought a new 2017 Corolla myself (everyone line up for the face punching) and plan on trying this app out to see what I can get from it, if $600 or even $400 is possible that will totally cover the cost of my monthly payment, even with paying income tax.