This all depends on the source of the leak.
It could be as simple as a leaking hose or a loos hose clamp. This would be relatively inexpensive to repair. Less than $50
It could be a hole in the radiator. This may or may not be an expensive repair. A smaller leak could be repaired with solder which would be inexpensive to repair. If the radiator needs to be replaced this could be an expensive repair.
It could be a leaking intake manifold gasket. This would be an expensive repair. It would cost several hundred dollars to have this repaired as the gasket set is relatively expensive and would require several hours of labor.
First, I would try some stop leak. You can purchase this at any major automotive parts store. There will be several choices. Don't go cheap. But even the more expensive brands will be less than $10. Just follow the directions on the container. You could get lucky and this is all it might take to stop your leak.
Until you get your coolant leak repaired watch your coolant level very closely. If you allow it to get too low you could cause major damage to your engine which will get very expensive.
Also, if you have pets keep them away from any coolant that is leaking on the ground. Coolant has a sweat smell and taste that could attract animals. However coolant is very poisonous. Even a small amount could kill a small animal. Rinse any coolant from the ground with plenty of fresh water.