I just purchased a base model 2006 Infiniti M35. It did not come equipped with a navigation system; however, it does have the back-up camera, bluetooth, and other features..... Is it possible to add-on or purchase an in dash navigation system or the navigation system software for the car?

Adding an Infiniti Nav would be major undertaking. Go aftermarket

Way too expensive. Go to crutchfield.com and buy an aftermarket unit