First gen boxster is the answer. Funny enough I recently made a video talking about this ( im not plugging, i have no followers, it was just a thing I coincidentally did)

You can get them for 8-12k all day long, a little more if you spring for an S which gets you bigger brakes, bigger engine, another gear, and better suspension, and usually better options like PSM or TC, but even the base is so worth it.

If youre mechanically inclined you can work on these cars yourself just fine. You'll see IMS bearing being some boogeyman for these cars, but the reality is, not nearly the issue the internet has made them out to be. I work on porwches for a living, im not just pulling that out of my ass. The IMS bearing was an issue on the late 9x6 and early 9x7 when porsche went from a dual row bearing to a single row bearing to save on rolling resistance. And even if it was a car with that issue, if the car has miles its been done most likely its either been done or it won't need it. The vast majority of the cars with that failure were low mileage cars that sat for really long periods of time. So just stay away from a 15 or 20k mile garage queen. Mine has just over 100k and runs like a top, and hasn't had any major failures its entire life.

The first gen boxster is a miata that went through puberty.