"Every contractor we talk to tells us its a great idea and they would pay for leads, but we have yet to have anyone actually purchase a subscription to our site." This seems like an obvious question, but have you explicitly asked them to give you money for the service? If not, then that is 100% ...
If the transaction happens on the same website, as the test, you don't need to do anything. The user has a cookie that attributes the version of the test to the revenue tracking in your testing software (Optimizely, VWO). Once you connect the Google Analytics with testing software, you should be ...