I think emmanelson96 meant to say they will "fight" instead of "right".
She is correct in that. Sometimes two turtles get along in an enclosure but too often they start fighting and have to be separated. Then they require two separate setups - tanks, filters, lights, etc - which gets expensive and takes a
lot of space.
A single turtle gets along just fine. It means he'll get more of your undivided attention!