Unique Loan type, need willing lenders!?

I have a buddy who is looking for a lender to do loans for constructing fixtures. His company installs these fixtures which will save his client money (without giving away too much details). These cost approx. $5,000.00 to install and will save the client on average of $300 per month. He needs to set up a way of getting these loans for construction where they would give him the money to produce the product and then the client would pay back the lender month –to-month. (Of course there would be a slight interest or increase of principal. They would be making monthly payments based on a % of their savings. This is very similar to the Solar Power loan programs. Does anybody know how to go about approaching a lender for this type of loan? What types of lenders would be willing to do this. Any advice or recommendations would be greatly appreciated. Thank you.