Inflexible Expense

It needs to do more stretching, clearly.

You borrowed money from a guy you met in an alley behind a pool hall. To pay back the debt, you owe $500 a week. He’s going to send big muscular dudes with no visible necks around to your house every Tuesday. You'd better have the money...or else. Inflexible expense.

In general, an inflexible expense is one that can’t be adjusted or skipped. You have to make the full amount, every time. The amount you owe to the neckless dudes, your mortgage, the bill for the regular medicine you have to take in order to keep your heart from seizing up...all those count as inflexible expenses.