Hi,
I have Tom Tom Navigator 5 wich includes maps of the USA & Canada. It really works well combined with a bluetooth GPS. Simple setup and easy to use. www.tomtom.com
Both got them off ebay and good prices.
Have fun!
GPS is free - you pay up front for the hardware and the corresponding software.
You may have to pay for upgrades to the software - map data specifically - but only if you want the lastest most accurate maps. BTW, the maps will not be 100% accurate as they typically lag behind by about 1 to 2 years. New areas or developments are where the lag is. However, it can be more then new areas as my house (20 years old) the address didn't exist according to the mapset people until 2 years ago. The street did, just not my exact address.
I'm not certain what TomTom would charge for a map set update but Garmin charges about $150 for the lastest DVD which many users in the Garmin sub-forum usually only upgrade about every 2 years.
You'll also need a large SD card depending upon how much of the country you want available at any given time as - Tom Tom used to take at least a 2GB+ in order to have the whole country, USA. You can easily change what segements go in and out on the SD card.