This is a problem. Did you try to do an h-1 transfer and it got denied because there were no paystubs. This is probably what uscis caught onto and asked for this to determine if you had an employer/employee relationship.
This is one of those RFE's that you have to really be careful, especially if you were out of a job before you filed AOS. Basically, the lawyer has to help you out in the response to make sure that you say you weren't paid but at the same time you stilll had employer/employee relationship. Be very careful, this is one of those RFE's where how you answer it could open up other doors which you don't want uscis to go through.