You'd be looking at hunting, fishing, and subsistence farming. Most crops will be hardy vines or bushes, probably fruits and berries. Hunting and fishing will be the main source of food. Deer, rabbit, racoon, armadillo, nutria (tastes horrible but they breed fast), duck, goose, gator, any kind of freshwater fish, most kinds of shallow-water saltwater fish if they're near a coast, anything that can be hunted from the comfort of a boat.
Culturally, they're going to be somewhat insular, staying to their own communities a lot, but ridiculously friendly once you open a dialogue.
They're always eager to ask someone to visit their family's home (most families live in one building or a series of close-together buildings) for dinner, which is always a communal event usually involving large amounts of food being prepped and cooked on the spot. Food is a VERY big thing with them, and they take pride in family recipes and the flavors they can evoke from the simplest foods. Many have their own spice gardens with dazzling arrays of scents and flavors (that may just be a southerner thing)
They're very giving, always glad to share some leftovers (seriously, i never leave my friend Jon's place without him talking me into taking a box of homemade jerky or venison. He'd have me take a whole side of venison if i had a freezer big enough) and they're always eager to help anyone who appears to need it. Whether it's building a building, digging a ditch, hauling in a day's catch, or tracking down a thief, the entire community can be expected to come together to assist, even assisting outsiders. They have a strong sense of 'we only get by because we're all friends'.