If you're in a place financially that you would consider a Porsche Cayenne for overlanding, I would say to consider the new Bronco sport. You can get a base model for the price of an almost 10 year old Porsche (about $25,000 per my brief searching) and the top Badlands trim is only a few thousand more, and you get the advantages of it being new. Being a Ford, the parts will be a lot cheaper and there's bound to be a good aftermarket for it within the next couple of years. Also used Porsches aren't known for their reliability. Say what you want about Ford, it almost certainly won't be in the shop as often as an old Porsche and will cost less than half as much when it is.