I recently had some financial aid problems as a college student so money that I was going to buy a regulator with is now got to go to school. But I was wondering about getting a used set on Ebay. I see a lot of older US diver, scuba pro, and aqualung regs for around $150. I realize you take a gamble on used gear but it may be my only option if I want to get a reg set. Are there any specific models I should look for? I need something for colder water but nothing below 100ft. Are there models to look out for? Has anyone done this route? How much did it cost to get the reg serviced? I mostly see SE3, Calypso, and Conshelf. If this is just a bad idea let me know. I don't like skimping on life support equipment but if it can be done safely I would like to know.