8 bucks isn't even going to buy a wiper blade lol, let alone your brake job. I'd plan for about $110 to do the job you need and not risk death or damage to you or others on the road or property.
You need to fix the bad line, probably all of them, seeing as rust has done its job and it was probably from the inside out. The kit I linked will do the entire car.
Do a flush twice and possibly rebuilding a caliper or 2 depending on how bad the fluid was/is and how bad the pistons are pitted.
If it was me, if replace all the lines under the car, pull apart the calipers front and rear and put new seals and boots on them and flush. Seals cost about 15 bucks for all, it's not difficult to do, some 300 grit sand paper, dot4 brake fluid and some brake clean, and the kit I linked. Brake fluid is only good for 2 years at best before the water content becomes high enough to start oxidizing internals.
Put a board under the brake pedal so it cant travel 100% otherwise you will kill the master as it has some crust down low and never travels that far.
There are some good diys here on this. All in all, $110 bucks ish and a weekend. Dont cut corners or you will be, not by choise when your brakes fail around the next corner.
