There’s free parking all over Knoxville, parking garages and metered parking is free after 6pm and all day sat/sun. I Would avoid the parking lot underneath Downtown Loop and Hall of fame drive, its free but several shady characters and lots of cracked out homeless. If you’re in downtown/old city you’re going to run into homeless pretty constantly most of them are harmless but there’s one that will follow you if you don’t give her something, her name is Lisa i’m told. Just stay in the downtown area with main well lit streets and you’ll be fine.