How Do You Determine The Profit Margin Of A Potential Local Lead Gen Client?

In episode 214 of our weekly Hump Day Hangouts, one participant asked how to determine the profit margin of a potential local lead gen client.

The exact question was:

On LLP you mentioned that one of the criteria for selecting a niche is to ensure the service provider has good margings to afford your leads – good profits. Question: How do you go about determining what profit margins they client would have as you explained with the carpet cleaning client you used as an example to drive your point.