everything in this discussion is relative to your experience level, the tools you have available, and your desire to learn new and exciting things.
most parts are readily available... but that depends on where you live. UK, good luck getting parts on your side of the pond (look to Germany). Canada, good luck getting affordable parts. USA... perfect location for easy to find, reasonably priced parts. Look at ROCK AUTO for rubber brake hose, and do not forget that there are five, not four hoses.
hand brake cable? yeah, the first one is a real PITA, but after that, they are fairly easy to replace.
frozen caliper pistons are prolly #2 on the brake failure list, followed by calipers that no longer float on their brackets. changing pads is time consuming but easy.
hard lines for brakes can be obtained at any hardware store, just be sure to ask for the right thread for european cars.
i would be more concerned about the presence of rust on a potential car. what do the shock towers look like? how about the underside of the rocker panels, and the floorboards (especially the front). severe rust is a deal breaker, mechanical issues just change the offering price.
literally all mechanical wear items are available in the USA for these cars. we enjoy a great deal of competitors for our restoration dollar.