Cost of waterproofing a basement?

My basement gets horribly wet when it rains, snow melts, etc. I am looking into waterproofing the room that leaks water in the basement so that it can be made into a living space. I want to be able to finish it off. I need to know a rough price before I get a company in my house because i don't want to waste their time if it is something astronomical. The room is approximately 15x20... Help!

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