I'm working on some bug fixes on web project for a client/friend. He has everything set up and working, but called me to fix a handful of bugs.
I've never used his system, I barely know how it runs, how it's organized etc and how everything works together. I'm going to need some time to understand this.
All this has to be paid for by him, generally how much time should be expected to understand his system? Is it uncommon to bill him for say a day or two if all I'm doing is understanding his system?