Once you learn the basics of turtle care, keeping turtles becomes relatively easy. One of the first things to know if you are new to turtle keeping is that you can't keep turtles in the small shallow glass bowls like you saw in the movie Rocky. To ensure the proper health for your turtles you must provide them with adequate space to move around. One other important factor is you can't just put them in a larger aquarium or container and leave them be. Turtles need to be able to get completely out of the water and dry off.
There are many other factor to properly care for your turtles as well including UVB lighting, heating the water and basking spot, water filtration, and diet. I don't want to sound like it is incredibly hard to take care of turtles and that you need to buy all of this expensive stuff. I just want to make sure that you take is seriously enough to learn and implement the proper husbandry techniques to help your turtles thrive.
As far as diet goes, things like cat food, and hot dogs just don't work well for your turtles. Diet can also range between different species of turtles as well. It is important to research the type of diet required for the types of turtles you elect to keep. Luckily for you, there are many commercially prepared turtle diets that are well formulated to keep your turtle happy and healthy with the proper growth rate.
Now let's move on to the proper lighting required for your turtles. Turtles are cold blooded, meaning that they cannot regulate their own body temperature. In the wild they use the sun to bask and raise their body heat. This is why you commonly see turtles sunbathing on a rock on a log. They also need to get vitamin D to remain healthy in captivity. Again in the wild they get all they need from the sun in the form of UVB rays. So you will need to provide your turtles with a heat lamp and a UVB full spectrum light source. It's your lucky day again because there are now a bunch of commercially available bulbs that accomplish both of these functions in one.
One last thing for beginners is that turtles are a little different type of pet than a dog. Most do not prefer to be handled too much and they can get stressed pretty easily. This is why it is best to observe your turtle eating, swimming, and sunbathing in the turtles habitat. Especially new turtles that you acquire, give them some time to acclimate before you interact with them too much. This will help to cut down on the stress of it's new environment. Stress in turtles can lead to illness and it is best to not have to deal with this, especially for a beginner.