I will answer the questions that have not been addressed.
Winter driver? Yes and no. I drive my Boxster in winter but only if there is max 3 inches of fresh snow. You have about 5 inches of clearance so you don't want to be dragging the underside in snow. So if the snow is too deep I take my wife's Camry.
If you drive in winter you must have snow tires(easiest on a separate set of rims).
Never been stuck in snow in winter yet.
Get receipts for work done. Plan on spending average about $1500-2000/year if you get the work done or less if you do it yourself. Yes I agree CPO is great and if Porsche dealer can give you an extended warranty great. I don't believe in paying for extended warranty though. I prefer buying privately because that individual is easier to negotiate with and they should have proof of servicing.
Don't buy a lemon. Yes a PPI is a must and use any weaknesses to bring asking price down further(believe me you will need the $$$$ later!).
Don't fall in love with the first one you see. Before you start the motor, turn the ignition on and make sure all warning lites come on particularly the CEL lite! Crooks may disconnect the CEL bulb to disguise a failing motor.
How are the tires?
Does the convert. top go up and down?
Any weird noises coming from the engine?
Air cond. works?
Elect. windows go up and down okay?
You cannot run a Boxster for the same cost of a Miata but then the Boxster is way more car. If you get a good one it can be great, a lemon will be a PITA! Enjoy the ride....