Lender wants to know where cash came from to pay off credit card?

[Mark Devens]

I'm trying to get an FHA mortgage for a $95k house. I have all the money needed to close, but underwriting wants to know where cash came from that I used to pay off a credit card about a month ago. $850 or so. I'm not really sure where it came from as I do a lot of side work on my own (scrapping, flipping cars, selling livestock). The problem is that nothing I do on the side is really able to be verified like a regular job because it's typically cash. What do I tell them while still being able to get the mortgage? Thanks!