If you want to put on 19" wheels use search and you'll find quite a few threads. The people telling you not to buy a Boxster are just trying to look out for you. It's up to you to decide what you want to do and what risk you are willing to take.
My daughter - 16 - will be learning to drive drive in my Boxster and my Escape hybrid. Why both? Because I want her to learn about traction control using a manual transmission. Even so I plan to send her to
Tire Rack Street Survival and recommend you plan on it as well.
Jsceash was spot on in regard to common money sucking issues. You may want to think about it in your budget. Any -
and I mean any car that has a single row bearing is one you should seriously consider getting the IMSB replaced. Or only look at cars that already have it. The dual row bearing (early models like mine) have less than a 1% failure rate.
One thing I will say is if you choose appearance - 19" wheels - over mechanics and make a poor or unlucky choice of your first Porsche, you'll wind up with a pretty roller that will not go anywhere. That's why people suggest the P-Car is not a good idea for a first car, can be a money pit, etc. Family mechanic or not, if he hasn't worked on a P-Car before you can expect him to need to purchase some P-Car specific tools and the P-Car is not like every other car out there. It's easy to screw it up, but if you buy the appropriate manuals, tools, and use the forum/Internet you can maintain it yourself.
One tool you will need almost immediately is a Durametric or if you are fortuante enough tto find one reasonably prices a PST2 or PWIS. Otherwise just turning off the airbag light will cost you a few $200 at the dealer. Just to give you a comparission an oil cahnge at the dealer is $285 out here. Doing it yourself cost about $75-100 (depending on oil type and parts).
Speaking of the dealer, if you buy a P-Car, go to
Porsche Club of America - Home and join up. One of the benefits is that most Porsche dealers will give you a 10-15% discount on parts and serice (sometimes). You get a cool magazine, the discount, and offers from your local club for various events. Inclusing DE (driver education) and autocross. Check them out. My PCA membership paid for itself with my water pump change. Plus the dealer prices have actually been less than those online. That one really surprised me.