Before getting you get a turtle you must ask yourself some questions. Who will take care of it ?   Who will feed it? Do I have at least 10minutes a day to feed, clean, and observe  it. Do I have enough money to buy all the supplies? Who will buy the supplies for it? like:

Aquarium

Basking Area

Light bulb (UV)

Full spectrum (UVB)

Heater

Filter

Food ( commercial food, beef heart, romaine lettuce etc...) 

If you can't answer these question with a yes or I can, it might be a better  idea not to get a turtle.

Here is a place where you can find most turtle supplies