Tinkering with a car will make it less and less a comfortable daily driver...
I'd urge you to save the $2k budget for rainy days with the current rebuilt-zetec. If you're in school already, you want a nice and fun car to tool around in, but you already know you need a dependable D.D. to get you through the education! If you can abstain from getting crazy about performance parts (which will tax the hell out of your income you can put yourself in a fantastic spot to pimp-out or buy whatever you want as a full time law professional! In the meantime, you won't need much to maintain a stock Focus... OR you could save for a good down payment on an ST! Sure you'll end up with a payment, but you'll also have a warranty and a turbo in the meantime for fun; AND a smog legal car for California! Once you get through school and start a career you'll either go crazy adding and tuning the thing or move up to something better.
I wanted to do the same thing in '03 with my ZX3, and before you knew it, I'd dumped ten large into it and the car got finnicky: it ran perfect, or little shit sidelined it.