OK, I am turning 31 and have a wife and 2 year old and I'm going to be getting a boxster next week. If you are getting the car in fear you won't be able to "enjoy life" later that's a bad idea. Yes it's good to get what you want, but remember, the more you can save now the better things will be later.
Had I gone by that philosiphy when I was 20 and put money away I could be buying a 911 next week instead.
Just do your best to get all the research done, not just the price of the car, and the price of maintenance, but consider the price of insurance as well. 21-30 is still a bad age for insurance regardless of discounts.
I did some research on maintenance and it seems this car will cost about the same, or less, than my 3000gt did. only $9.00 per spark plug compared to $14.00, only $260 for a clutch compared to $350 and up.. I'm pretty sure wear items aren't expensive, but the cost of labor is what is going to rip most people apart. If you are considering a high $$ car like this, think about picking up a service manual and learning a little bit about doing your own work, it saved me thousands upon thousands of $$ on my 3000gt...
Good luck with the purchase though, if you decide to go that route. From everything I've read, and every car I test drove the boxster seems like it's the right choice for everyone.
Oh, and when it's time to have a wife or two and a kid or two you can always buy an old honda or something to toss the fam in.