Russ: You certainly have carved a niche with taking as much control of the project up front. This makes your service much more comprehensive. That's basically how we did business over the last 15 years of our run. We took control of a large portion of Community Banks and Credit Unions Ad budgets. We'd provide jingles, copywriting, TV production, media buying and newspaper advertising. We'd get money up front for a particular package. This would give us operating capital. Unfortunately, the jingle business became very competitive and was difficult to get any money up front. Plus prices were dirt cheap.
Good luck with your current business model...sounds like you got a good thing going.
JM