mining btc is the business of asic buy some bfl and pray the deliver. bummer because the price just doubled, delivery this summer, when
to mine other cryptocurrencys it's a more complicated affair, if you like to solve problems then it's ok for you. Just look for the thread that talks of the 10$ plastic case and it will tell you how to build a well ventilated case for your computer farm.
with 5000$ you can build 4 computers of 3* 7970 cards each plus mobo cpu ram hd and case each. Look at the hardware thread ans you'll find one with the basic starter kit.
IT WILL RUN HOT, you need a well ventilated place with a good AC or 2, but free heating in winter.
Me I mine with my old GPu and maybe i'll buy a 7950 or 2