I bought one of those DIY Hoover cleaners a long time ago. It works OK, but not as good as a rental or a pro. It's good if you have small areas and just want to keep up with them every year or two.
The Rug Doctor rentals seem to work pretty well, but be careful. Sometimes they are not very clean when you get them and it's pretty nasty to think about what they just got finished sucking up in someone else's house or apartment.
I've had the best success with the pros. The do a pretty good job of spot cleaning first, getting the right amount of cleaning agent into the carpets, and the biggest thing is that they do a good job of extracting water back out of the carpets so they dry more quickly. They guys we've used in the past do a lot of commercial work and do residential as side jobs.
Make sure to put something under the furniture legs (like double-folded aluminum foil) if you move furniture around. Otherwise the damp carpet might stain in those spots.
For a 2 BR apartment, I'd just rent from HD or Lowe's. Vacuum as deeply as possible, first. Get a spray bottle of the spot cleaner to pretreat anything you think needs it, then hit it all with the Rug Doctor.