Yeah...not all models came with an SD card reader. But you can always get one of those cheap USB SD card reader adapters for it. You certainly wouldn't want to pass up a great deal on a MBP if it didn't have the card reader.
As far as where to look for MBP's for sale...what's:
- your main priority...new, used, refurbished?
- how new or how old of a MBP model will you consider?
- what is your "real" budget? And please don't say as little as possible!
New: Sure you can buy a new Apple product at most electronic stores...but I always felt that if you're going to buy new computer...you might as well get it right from Apple.
Refurbished: Again Apple is your best choice (IMHO).
Used:: E-Bay & Craig's List...with my preference being Craig's List, since you can see it & use it before buying...but your selection at any one time is limited. With e-Bay you have much more to choose from...but you will probably pay more for it due to the Nationwide audience...and you don't get to see & use the computer before buying.
That's really about it. Most other online places that sell used Macintosh computers really charge an "arm & a leg" for what they're selling!
Hope this helps,
- Nick