The unit comes with a base map, that only has major roads and highways. Not all that useful, really. Your unit has 24MB of internal memory, and doesn't take expansion cards, so you have to select what map segments you want, and may need to overwrite them with different segments if you want to use it in a different part of the country. Since your unit does do auto-routing, I'd suggest the MapSource City Navigator North America (assuming that's where you're located).
Thanks for the info