As with probably every occupation or profession, there are good things and not-so-good things about being a mobile notary. I'll touch on some of them here.
First, the good: You get to meet lots of very nice people. When you're with them, there's usually plenty of opportunity for friendly, often-engaging conversation. You get to travel to many different locations to perform your work. You're not confined to a routine 9-to-5 office job. You enjoy the independence of setting your own work schedule. You can accept only the jobs you want, and refuse (better yet, refer) those you don't want.
And the not-so-good: When the weather is cold and windy and rainy, driving around all over the place isn't exactly fun. If you're looking to get rich, this isn't the business for it. You can do okay if you apply yourself, but it's hardly the most lucrative-paying job you could choose. You're competing with gazillions of other notaries, many of whom advertise unrealistically low prices solely for the purpose of attracting unsuspecting clients. (Of course, those clients soon learn to their dismay that - as with most things - they get what they pay for!)
The bottom line: If you enjoy the independence of setting your own schedule, driving, meeting and talking with people, performing a much-needed and highly-beneficial service, being a mobile notary public could be a good fit for you. And if you also have another job, you can use your mobile notary service to bring in some nice supplemental income.
A word of caution: If you don't enjoy driving, you probably won't enjoy being a mobile notary. It's really not feasible to attempt this type of work using public transportation. Also, if you're not comfortable being out alone after dark (especially with strangers in unfamiliar areas), you might want to consider limiting your service to daylight hours only.