2001 Mazda Tribute Oil Leak

I just repo-ed a car that was in my name that my cousin recently stopped making payments on. I don't know too much about the car. But when I finally got it home and moved it from my driveway to the street I noticed a small puddle of oil. It had only been there maybe 24 hours. Not knowing much about cars at all. What am I checking first? What would it most likely be and what kind of prices am I looking at to fix this before I sell it?