1990 Nissan Maxima Please Help!

I bought a new battery then the next day my car wouldn't start all you could hear was a click then no power in the car. So I cleaned the connection to the neg cable and the car would start. Now anytime the car is turned off there is no power to the car, even the horn doesn't work in order for anything to work it has to be running. When the car is started everything like the clock and radio is reset I was going to buy a pos cable but it is a speciality item running at $100 so I want to see if it could be something else before I buy a cable for that much the cable has some connectors on it that go to fuses or something. Thank you so much for any help you can give.