Your biggest risk with buying is how much time it would take to sell it. There is no way the depreciation over 6 months on a 6 or 7 year old used unit would come anywhere close to rental costs for a six month rental. But, you may be time crunched at the end of your trip and if it took 3 weeks to sell it, that could be a big problem.
I stayed in a park a couple of years back on the pacific coast. They also have numerous rental cabins. They were close enough to Sea-Tac airport that they got a lot of overseas visitors who were at the end of their vacations. The park owner had a big sign saying he would buy your car for cash. I asked about it, and he said that many foreign visitors (especially young people on college summer break) spending a couple of months in the states would buy a cheap used car when they arrive, drive it for the duration and then just abandon it at the airport. He figured why not offer them a few hundred dollars and a ride to the airport and resell the cars. He said in a good year, he might end up with 20 or more cars, all bought for $500.00 or less. Said he averaged over $1000.00 profit per car. Buying, using for a few months and then selling is not as rare as I first thought.
