The salary of a notary would depend on the location, the notary fee, and the overall number of signings the professional managed to complete.
The notary fee will vary depending on the state, it can be anywhere between around $2 and $15 per signature.
Typically, notaries can earn about $30.000-$60.000 per year.
Mobile notaries can charge a travel fee in addition to the actual signature fee.
Many notaries also offer other services (like tax preparation, insurance selling, and so on).
Bear in mind that the expenses can be great as those include insurance, journals, various forms, annual background checks, training, exams, etc.