whoever gave you theses ideas are either dumb or lying, or both:
1. buy a rental car - rental cars have the most suspicious driving records. many people don't give a damn about driving a rental car carefully. in short, they tend to abuse rental cars. by all means, don't buy a rental car. it's worse than marrying a whore.
2. rental car for interstate travel - unlimited mileages don't apply to interstate travels (except for a few neighboring states) most of the time. try to rent a car to drive from new york to florida with unlimited mileage, you won't find it, unless of coyse, you lie to the rental company where you go. then you'll probably get into bigger trouble if something happens and yor car isn't covered by insurance due to violation of contract. in short, don't listen to the liars.
3. buy a harley, seriously, for personality statement, or any japanese car for practicality. what's the point of other cars anyway.