That is an open ended question that can go in many directions. If you haven't read thru this link already, it's a good place to start.
http://986forum.com/forums/boxster-general-discussions/14685-thinking-buying-boxster-must-read.html
There are several YouTube videos (Boxster specific) that might also help.
The common answer is to buy the car with the best documented maintenance records you can find. Then have a trained
Porsche mechanic give it a thorough inspection, +/-$400.
For $7,000 in LA, you are going to get a middle of the range car that is going to need work to catch up on the maintenance probably. Parts can be very expensive and Porsche mechanics earn their keep. How much of the work can you do yourself? Consider reaching out to a local PCA chapter. They can be a great source for advice, cars and mechanics. PCA Owners tend to take decent care of their cars also.
Take your time and leave your heart at home. Welcome to the group and good luck with your search.