73 duster front brakes locking up when coming to a stop.

When I bought the car, the guy stated that the front brakes were locking up. But I didn't think that would be a big deal. Or a deal breaker when I purchase the car.
When you drive the car, if you push on the brakes slowly it will stop if you use the brakes. Normally the front will lock up , but as soon as you let off the pedal , it rolls again....