Hello, I am working on a paper concerning reasons that Caesar would need to have a decisive victory in Gaul, and I wished to discuss that he was in debt and victory would bring money to him.

I read all over that he was in debt, but I can never find references to specific sources. I need a primary source or a secondary source that will reference or argue why he was in debt.

If he really was in debt, where does it say it, and if he was not in debt, why is it so commonly stated?