a new business idea using GPS to make maps

I am wanting to use my Magellan Map 330 to do some rough site analysis in the field and use it to calculate areas and make notations. I want to save this info and import it into a drawing format such as .dwg and make site analysis maps and drawings. Does anybody have any experience with doing something like this ? What software have you used and what do you recommend ? Do you think 60 $ an hour would be a fair price ?