You want to know all the items or services that the MSB has that would bring in cash - as they would use that cash to fund the check cashing. When you are trying to balance Cash Out vs Checks In, these other services would factor in.
Do they sell Phone Cards, Hot Foods, Lottery, etc. I have had MSBs that sell those items plus fishing gear, clothes, pottery etc. What they sell depends on where they are located, the size of the operation and who their clientele are, etc.
If the MSB is in a gas station, how many pumps etc.
A good rule to have is for the bank to dictate what you will or will not accept in your check deposits, e.g. checks payable to corporations or entities, or perhaps put a dollar amount.
Just a few thoughts