Transport to get around the island for two months

Hi I'm going on an internship on Menorca in Mahon. I would live in Arenal d'en Castel and I don't know how to get to Mahon and back every day without taking the bus. Is it easy to just buy a cheap old banger of a car and drive that around for the time being? But where would I find such a car or motorcycle perhaps? Is there another website, that I could check out, where I could buy second hand stuff? Thanks for helping out. ;)