Wow rick, I know a few shops that would LOVE a sales person that could bring in 500k in sales ... sadly I've never seen a small to medium sign, marketing or graphics shop have a sales person come in and do that much unless they pulled their old customers over from a shop that was closing its doors ... and generally if a sales person is doing that ... the owner is on his/her way out the door due to health.
As for the questions from the OP ...
1. from other sales positions ... doesn't matter the business really. If you find a good sales person, as the saying goes ... they can sell snow cones to eskimos. You just need to make sure the market can sustain the sales to be commission only. When I used them was almost always when I needed to approach corporations for their projects in their internal image (wall wraps, corporate art, etc) and was almost always teamed up with interior designers. Temp sales position I gave a 30% share of profits from the jobs and was generally for some wicked sales people that could get me the sales I couldn't get due to my lack of time to invest in them.
2. making sure they have the marketing materials to properly sell your services, as well as having the ability to match their sales they generate helps as well.
Really though, most of the commission sales positions I see rotate rather frequently ... doesn't matter the industry they represent ... mainly due to the fact that it's a fickle market and again, sales need to be there to sustain commission only. Here in the north of Texas seems like one out of every 10 store fronts is a shop that offers 'signs' and will be happy to underbid the next. I know that is a little overly inflated for a statement, but on the way to one of my in house design jobs I do ... I pass 2 places that do things like tinting and 'graphix' but try to be normal sign shops as well as a more than a couple sign shops that compete with each other but are about as employee friendly as a punch in the face. As such I don't see very many outside sales positions, most are internal ... get paid minimum wage and earn a tiny commission to encourage sales. The few outside sales positions I do see every year is from companies that offer creative services that advertises for a 'graphic designer' but requires that position to be outside sales and general shop ***** with 5% commission on sales as compensation.
Even had one job I applied for about 6 months ago for snot and giggles for a 'graphic designer' that didn't even want to see a portfolio, and even after I sent in the resume they wanted ... got a 9 page 'application' pack that included not only an nda, a credit check authorization form, request for driving record and a 2 year non-compete agreement if I stop working there for ANY reason for any aspect of graphic design in any industry ... for a $10/hour position they described as an outside sales role that would garner no over time, expected to be selling at $90k per quarter after 3 months and had no reimbursement for expenses (gas, wear and tear on vehicle, cellphone, etc) and would require all design work to be done on your own equipment. I don't know about you ... but that sounds like a bad deal.
Not the only bad deal I've seen for employment. But again, depends on the area.