Sales people at UPS start out as Sales Reps and the salary isn't that great. They are considered to be specialists. If they can get promoted to Account Executive then they become part of management as either a grade 13 or 14. That's when the salary picks up plus there is some commission involved. Just like every other job at UPS, the sales people work under high pressure and almost unrealistic goals. The turnover rate is very high because of this.
They spend most of their day either calling customers or visiting customers. And yes they get paid for their mileage. Every employee at UPS gets paid for their mileage (I did when I was in TSG).