I'm also a student and I initially started with a 33g reef tank... I count myself very lucky, as my initial startup cost was quite low. Nearly everything that I got, I got used.
33g tank and stand - $50
2 holes drilled - $20
Glass for overflow - $10
15g sump - $10
Acrylic for baffles - free out of scrap bin
Mag 9.5 (new) - $180 (I think)
2x96w PC fixture (new) - $240
~70 lbs Base rock - free (I just needed to clean up the tank that it came in)
~10 lbs LR - $50
Bakpak 2r Skimmer - $150
Total Startup cost: $710
My first few frags costed me nothing, or only a few bucks. Many people around this board are very generous.
I upgraded to MH lights later using ballasts that I got an electrical wholesaler... MH upgrades cost about 300-400 dollars including bulbs and 36" PFO reflector.
Later on, everything got moved into a 24" half cube and new 17g custom sump. That move only costed me two tubes of silicon, $50 worth of lumber, $20 worth of paint, primer and screws. I managed to sell off my MH setup and got myself a pendent and hqi ballast for maybe a few dollars more. I built my new skimmer for pretty cheap (considering size and its skimming capacity) as well.
Doing things yourself will save yourself a bundle if you do it correctly. Just keep an eye out, not just on aquaria forums, but on everything in general. If you're lucky, you'll usually come across something that can be used in the aquaria world... My girlfriend's father was going to through away sheets of 1/8" acrylic... I managed to save that, laminate them, and made my skimmer that way. I got some glass for cheap, and built my own half cube with 100% silicon that you can get at Home Depot for 6 bucks a tube. I built my own stand, which saved me a bundle.
In total, after counting all that I've bought, and all that I sold... I probably spent around $1000 on my setup and upgrades. Not bad for a student who only works full time 4 months out of the year and 8 hours/week during school months
-Rich