The first thing you need to determine is if it is even legal for you to keep the turtle. There are a number of species in Florida that you are not allowed to possess and a few that you can have, if they are captive bred, but can't take from the wild.

The next thing to determine is if you should keep it. The short answer is probably not. The longer answer follows.

If you have never kept a turtle before, and I assume you haven't since you are asking, now probably isn't the best time to learn. Some turtle species, especially older individuals, can be difficult to acclimate to captivity.  Others have specialized needs and diets. You don't want the animal to suffer or waste away while you learn.

Often the turtles you see crossing roads and yards are females looking to nest. If placed in a situation where there isn't a suitable nesting area, she may void her eggs, which doesn't hurt her, but wastes the eggs. Or, she may retain them and become egg bound, possibly leading to her death.

All turtles are long lived if cared for properly. I know of examples from many species of turtle and tortoise that have lived over 50 years in captivity. They are definitely a long term commitment.

Keeping turtles properly isn't cheap. Even if you buy the turtle, the turtle will be the least expensive part of the endeavor. If kept indoors you will need a stock tank or aquarium, aquarium heater, UV and other lights, a filter, and material for inside the enclosure. Outside you will need a pond, landscaping, and have the whole thing protected against predators (dogs, coyotes, cats, foxes, raccoons, skunks, rats, crows, etc.).

I appreciate that people have empathy for animals and see a turtle in trouble on the road or find a hatchling in their yard and wonder "what chance does it have". Yes, the odds are against it, they always have been. Our roads, fences, parking lots, and outside pets have helped make the odds longer. You can improve things by helping the turtle on its way, but if you decide to keep a turtle without knowing what you are doing, then you aren't doing the turtle or yourself a favor.

As evidenced by this website I am not opposed to people keeping turtles. I just suggest they go into it with their eyes open. Check out this link Turtle Book. It is available as a free download and if you later decide you want a copy you can hold in your hands, you can buy one at the link. Read through the book and if you decide you still want a turtle then find one through a breeder. One of the most valid justifications of breeding turtles is, if done properly, it reduces the number of turtles taken from the wild.

"No," said the little prince. "I am looking for friends. What does that mean — 'tame'?"

"It is an act too often neglected," said the fox. "It means to establish ties."

"'To establish ties'?"

"Just that," said the fox. "To me, you are still nothing more than a little boy who is just like a hundred thousand other little boys. And I have no need of you. And you, on your part, have no need of me. To you, I am nothing more than a fox like a hundred thousand other foxes. But if you tame me, then we shall need each other. To me, you will be unique in all the world. To you, I shall be unique in all the world..."

...

"Men have forgotten this truth," said the fox. "But you must not forget it. You become responsible, forever, for what you have tamed."

Excerpted from The Little Prince