Red eared sliders are among the easiest to keep, and are usually available locally. I'll give you an overview on care so you'll have an idea of what you're getting into.
Turtles need certain types of lighting and need to be warm. Theymust have a basking area where they can get out of the water, dry off, and bask in very warm light. The ambient air temperature in the tank should be around 75 degrees, with the basking area warmer still. Over the basking area there should be some sort of lamp that will take a 40-60 watt incandescent bulb (or you can buy a ceramic light fixture made just for reptiles). If you live in an area that has farm stores, you can buy a metal light fixture made to keep baby chicks warm for just a few dollars. Don't buy the accompanying bulb, however. You need an ordinary incandescent bulb in the basking light.Hardware stores have similar inexpensive fixtures. The basking area should be kept at 85-90 degrees. Use a thermometer to be sure. You can adjust the temperature by raising or lowering the light fixture. The lights that come with the covers aquariums are not suitable for turtles. You'll also need a submersible aquarium heater that will keep the water 78-82 degrees.
It's extremely important that you buy an additional light that produces UVA/UVB rays. Make sure it provides UVB rays. Don't take the word of pet store personnel, but read it for yourself. Full-spectrum is not the same thing. I'm putting a lot of emphasis on this because it's crucial to your turtles' health. Without this light, Metabolic Bone Disease (MBD) will develop because your turtles won't be able to produce vitamin D. Vitamin supplements are not a good replacement for the proper lighting. MBD causes a very slow and painful death. UVB bulbs must be replaced every six months as they lose their effectiveness after that, even though they may still look fine.
A 15 gallon tank is usually the minimum recommended for babies, and they quickly outgrow that. One adult turtle will need a 60 gallon tank (larger tanks are needed for multiple turtles), so you may want to get a large one so you don't have to keep replacing it.
Turtles are very sensitive to water quality. Even if you change the water every day, it can still contain harmful chemicals. A good filtration system is essential. Water changes are also needed even with a filter.
Feeding is an area where pet stores often give out bad information. Commercial food should make up 1/4 of the diet. Animal products (meat, earthworms, canned cat food) should make up another 1/4. The remaining half should be plant foods (dark lettuce like romaine, bits of strawberry or melon, etc.) You may want to look at these sites for additional information on care and feeding. I especially recommend that you check out the lists of appropriate foods.
You may also want to check on laws concerning turtles in food establishments. They do often carry salmonella bacteria.
If you have further questions, just let me know by clicking on REPLY.