I owned 3 Porsches, 2 of them Boxsters. My experience with the later versions were that they were as reliable and as cheap to maintain as a Honda of the same era.
But as with everything, your experience may differ. A lot of the maintenance can be done yourself with online instructions and a few special tools. Even oil changes can be done at a fast lube place if you supply the right parts and even the right oil.
The significant expense will come if there is a major accident or engine/transmission repair needed. But the cars are rated reliable, so no more probability than any other car.
You are looking at 981 series cars, very different than 986 or 987 in terms of build quality. Do the common sense things like warming the engine up gently for the first few miles. 7 miles is about where the engine will be warm so oil changes at least twice as often as Porsche requires would be a must for me.
Is there a independent mechanic who works only on Porsches around you? Look on
Independent Porsche Repair | Repair Shops Specializing in Porsche | PCarShops.com.