Yea you can definitely be a professional driver for either the mayor or some other high end official or business owner. If you really want to, I recommend buying a company like the Downtown Cab Co. and have it appraised by one of the admins. This would allow you to make your own cab fares and possibly have other drivers working for the business. Once you have the company, you can then run your cab service for players who don't have vehicles yet, or just need a ride, and run you limousine service as well for wealthy individuals.
