brake fluid is leaking on 1999 Dodge Grand Caravan

How many possible things could there be for the fluid to be leaking?

Need to have a tech troubleshoot where the leak is coming from before anyone can give a estimate for repair
front calipers, rear calipers or wheel cylinders, master cylinder and the brake lines depends where you see fluid ( behind the wheel? under the hood? )
How many different possibilities are there?