Aquatic turtle questions?

I was think about getting turtles again...bcuz mymom sold my others one day while I was at school. I had a eastern painted about 1.5" and a RES about 3.5". Now I am thinking of getting 3 res babies online from turtlesale.com for $12.95! I was wondering if these are good turtles to get and if not what are any better ones? I want to get two atleast but I don't wanna spend over $75 just on the turtles. I found a 10 gallon tank for $26 at walmart with a light and a filter . I know the rule is 10 gallons per shell so I would need a 30 gallon tank atleast. Are there any good websites where they have good deals for tanks that size? And any RES info would be appreciated. Do yellow belly sliders make good pets as well? Any info on them would also be appreciated. Thanks in return!