Your master cylinder is shot. There is probably nothing wrong with the brake booster. Driving without power brakes on disc brakes is very dangerous. You can usually get rebuilt master cylinders from parts stores for around $50. You can also rebuild the calipers easily and fairly cheap. I think I only paid about $20 for a rebuild kit from Toyota, enought to do both sides. BTW these problems are more age related than mileage related. Over time rubber hardens and won't seal no more. Common problem on all old cars.