I don't know. Life is short, what have you got to lose? You can't lose your house cause you don't have one yet
I have bought and sold a lot of cars over the years... close to 100 by now. Some were good investments, many were workhorses, some were pure joy. Few have brought as much joy as this little 986. The Boxster is a still lot of car for the money by any measure. If you had a wife and kids depending on your sober choice I might feel differently. As it is you have little to lose from the experience. If the car fails you can ride a bike, take the Nike highway, work weekends, get her fixed up again, no worries.
I drove a 69 Datsun Roadster briefly in college. It required almost daily tinkering to keep the carbs in sync, and it was totally impractical for my lifestyle at the time, but I loved every minute driving it. You are handy with tools and you are going into this with your eyes wide open. I say follow your heart even if only for a little while. The reality of responsible adulthood will catch up to you soon enough.