brakes

How do I find out where the brake line is leaking...don't have a lot of money to pay a repair shop

You just have to look for it. Thats what they would do no matter where you took it. How old is your truck? How much fluid are you leaking> Probably the first place I would look is the master cylinder. Another common place are the rubber brake lines. One at each front wheel and one on the rear axle housing.