Not that I am recommending a first timer do it, but I ONLY rent "friends" vehicles. Most of the time they are motorcycles, but several times I've taken friend's cars to pick up people up in Negril and Mobay. I'm about to head to JA for 6 weeks and already secured a nice new Honda 125 for the whole time, the price was $125 for a laptop off Craigslist.
Please be aware that there is absolutely no insurance coverage that would be in effect while renting a "friends vehicle". As previously mentioned, you would be responsible for any and all damages that would be incurred should there be an accident.