Please do a ton of research! I have kept many species of turtles and bred them, and this is a species that can be difficult to care for. Please know that you need 10 gallons for each inch of turtle, and female RES can get very large. You will also need a filtration recommended for TWICE the tank size, because turtles are dirty critters. I have never kept RES in tanks past babyturtlehood, I have a completely enclosed and escape proof, and very large, pond for my happy turtles. RES also love deep water, but also need a place to bask under a GOOD UVB light. Without this and calcium supplements, they can develop terrrible problems such as MBD, a bone disease, or soft shell, resulting in death.
RES also love a largely varied diet.
Anyways, good on you for rescuing them, though in those situations I tend to try to just walk away, because if you buy them, they will buy more turtles. Its hard though I know. You may want to find someone who is better equipped to keep and house them, unless you feel you are up to the task. If you are, I wish you the best of luck! I love turtles, have as long as I can remember. I have one stinky old turtle who I hatched out when I was six. Well he's really not that old ha, for turtles anyways.
If you don't want to tackle such a difficult species but still want turtles, I would recommend a mud or musk turtle. My person favorite is
Stenothernus oderus, the stinkpot musk turtle. Extremely hardy, and they stay pretty small. Pretty inexpensive too.
Enough of my blabbering, feel free to pm me anytime if you need any specific help.
Edited to add: Oh about Salmonella. While there's no telling if these turtles have it now, its not really a huge issue unless you feed your turtles raw chicken. You should always take precautions and wash hands after handling turtles or anything from their tank, though, just for safety!
