For concerts, you basically need two things: a camera that handles low light well, and a lens with a wide aperture. If you're on a tight budget, I'd recommend getting a used DSLR or mirrorless camera - Canon EOS M50 Mark II, Sony A6400, or similar models. They're older, but still great for beginners and way cheaper than new gear. But here's the thing - the lens matters more than the camera itself. A kit lens just won't cut it for concerts because it doesn't let in enough light in the dark.
Save up a bit and get yourself something with f/1.8 or f/2.0 - like the Sony E 35mm f/1.8 or Canon EF 50mm f/1.8 STM. It's not expensive, but it makes a huge difference when shooting in bad light. With a lens like that, you can keep your ISO down and your photos won't look nearly as grainy. Start with something affordable and see if the hobby sticks - you can always upgrade later.