That's a great plan. Used cages can be a good bargain, just be sure to clean and properly disinfect the entire cage before bringing it around the bird. I use a pressure washer, with a bleach/water mixture. Then I make sure it's rinsed well for at least ten minutes. Then I use a quarternary disinfectant (hospital-grade disinfectant) and make sure the cage soaks in it completely for a minimum of five minutes. Disinfectants must remain wet on surfaces for at least 90 seconds to properly kill bacteria and viruses, even your household cleaners for regular cleaning.
I know it's hard being a student, money is always stressful, but I'm sure we can help you find the right cage if you end up keeping him. Best of luck!