I do a bit of business this way though the local printing companies.
I give them my "suggested retail price" and my "re-sellers price" in my quotations.
A LOT of these companies are shopping around, so be ready to lose some of the printing (especially at first) to the online wholesale printers.
The benefit that the company gets from using you is what you need to be selling them on, as there will always be someone cheaper. Some potential "clients" will never look past the dollar point, so let them go that route & forget about them.
Some will get frustrated with not being able to talk to someone specific. You have that going for you.
Some printers normally just print what is sent without any checking colors, etc. Many jobs sent to us by these "professional designers" have incorrect colors/sizes/resolutions/etc that we check and notify them or fix & print them. This makes for a much happier customer.
Most of the wholesalers have longer turn-around times than the smaller shops. We turn many projects around in 24-48 hours, so when they get an emergency/rush order you can satisfy that need.
Another good point of having two local companies working together is that you can both send business back and forth. If they are an offset printing company, then use them for your customers who need business cards. This will help them steer more business your way also.
I'm sure you have other "advantages" to you & your shop that you can sell yourself with.