Optimal business model when capital is tight?

Hi monkeys! 

I've been thinking with an entrepreneurial cap recently and have been trying to figure out a business model that would optimise return on capital invested under the assumption of limited capital. 

My initial thoughts have landed upon an agency style business model. Essentially a middle man between a provider and a client. The business would essential only handle client acquisition and take a fee from the provider of the service. This model would only require sufficient capital for marketing and SG&A. 

Which industries does this business model work best in? 

Am I missing something?

Cheers!