First of all, congrats on the baby and on your decision to breastfeed! I was very nervous about supply, and didn't want to fork out all the $$ for a fancy pump. I bought the Playtex - Petite Double Electric Breast Pump which sells for ~$80 at Walmart (or, get a 15% coupon at Babies R us and it's less). It's probably the cheapest electric (double) pump out there. Anyways, it worked fine for me. I only double-pumped a few times (takes too much coordination) and just set it up for single-pumping the rest of the time. I started when my girl was 4 days old and she self-weaned at 11.5 months. Fortunately, I never had a supply issue and after ~4 months, only had to pump 2x a day to get all the milk she needed for the next day (she started daycare at 2 months old). I even pumped enough to send off nearly 700 oz to a Milk Bank! One little adapter piece broke right away (I was really rough with mine--never used a case or anything) and one of the plastic handheld parts of the pump broke after 11 months (I dropped it one too many times). Also, it fits the playtex bottles, so I liked to pump into the Playtex Vent-aire bottles (or directly into the drop-in bottles/liners)! Very convenient! Overall, for the budget-minded mom, I would definitely recommend this pump!
Also, like someone else said, there's no reason you can't look for a used pump. Just be sure to sterilize all of the parts before you use them. Check out Craigslist, or whatever baby consignment or specialty stores are in your area.
Good luck!