Unfortunately, the previous owner had a dog living with him that wasn't properly trained to do his business outside. As a result, we inherited a house that smelled like a zoo.
My dad stopped over and gave us a great tip. Take three large cans of inexpensive coffee and a box of Tide and spread it over the floor. Leave the mixture on for three days than sweep/vacuum it off the ground.
It will absorb the smell. And let me tell you, it does! We noticed it working almost immediately. A very handy tip for anyone who has that aromatic house scent of ammonia.