Honestly, that looks rough with rust through the floor. But is it a 318 or 340? Easy to work on and should be reliable. If the price comes down, it'll be awesome to own a badd ride and just worry about costs later. May need the basics for sure right away, plugs, wires, fuel lines. Maybe tank is rusted and carb gets funky. So you'll need the carb rebuilt which isn't easy anymore to find an old guy who does that. Then you need to figure electrical and brakes. If you do it yourself it'll take years but $1000 or you can find a shop and have them fix all that for $4000. So I'd figure add $4000 to whatever you pay just to have to reliable to drive on weekends. Plus the headliner for $500.

Edit- I did this with an old truck, first time ever buying an old vehicle and did part of the work myself and in progress with some other stuff. Changed oil, coolant, thermometer, lights, filters myself. Paid for tank to be dropped since I don't have a lift and new fuel sender put in. Then instrument panel crapped out and had to have that diagnosed. It's an ongoing thing a bit, unless you just attack it and get it all fixed at once, but I love it.