With turtles I actually prefer to use really large rubbermaid-type bins instead of glass aquariums. Aquariums might look a little nicer but they're expensive, heavy to move, and a pain to clean. My camera has no batteries at the moment but my turtle lives in a large bin with a big rock as a basking spot and a cave to hide under (my turtle is a mud turtle and they love caves). A lot of basking lights can be clipped on to the side of the tank/bin. Mine has a broken clamp so I have a screen top laying across the bin that I put the light on. A RES will require a strong canister filter and that shouldn't be a problem in a bin, either.
Since RES turtles are very messy and require a lot of cleaning, definitely look into making a bin enclosure
. By the way, I like to keep turtle tanks bare-bottom (no substrate). It makes the tank even easier to clean.
If you do decide to use a glass aquarium, check craigslist for cheap used ones.
