Although wild turtles have been historically kept as pets, Turtle Rescue Team strongly discourages removing any healthy turtle from their natural habitat and housing them as pets in captivity. Though they tend not to show it, turtles can get extremely stressed in captivity and are also prone to nutritional deficits. Additionally, turtles can spread infectious diseases to people most notably Salmonella. Please release any healthy turtle you find back in the location it was found.
If you are interested in owning a turtle, there are various organizations that adopt out non-releasable turtles.