Park on a slight incline, put it in neutral, then release the brake pedal and see if it creeps ahead on its own. If it doesn't, suspect sticking rear parking brake cables or a sticking front caliper. Put a block of wood downhill a few inches in front of one of the tires in case the sticking brake lets go, then crawl underneath and flex the parking brake cables. That will usually make a sticking cable release. If it does, have that cable replaced.
If neither cable is stuck, jack the front tires off the ground and look for one that you can't spin by hand. If a caliper is sticking, it is customary to replace both of them at the same time to maintain even side-to-side braking.