Seems like a lot of people here don't know jack about cars so I'll help you out with some solid advice.
1) The Boxter gets good gas milage, its a very small 6 cylinder engine, non S versions are 2.7L if I remember correctly.
2) That year Boxter had a problem with the main seal and when this goes it costs a fortune to fix because of the baller mark-up on Porsche parts and service added to the fact that this is an expensive repair on any car.
If you can do the work yourself then go for it, but if you can't do much more then change oil I wouldn't get a 10 year old Boxter with 71K on it. It's a great car, don't get me wrong, but even I, with my extensive experience in working on cars, wouldn't buy a Porsche without a warranty or very low milage. This isn't like getting a 10 year old Toyota or GM where any local shop can fix it.