Service Contracts for commercial carpet cleaning??

I recently purchased a commercial carpet cleaning biz with long standing relationships with recurring work commercial clientele.  They have seldom used contracts in the past and the few they did expired a while ago (still actively working on those accounts though)

I see value in establishing contracts for present operations and to build value for a potential sale later.

Anyone have experience shares and insights?  I'm interested to learn how to position and structure service contracts where the frequency and scope of work is typically variable.  

I appreciate any help from the community!

Ben

Satisfaction Plus Carpet Cleaning

Milwaukee, WI