I knew of several charitable appeals who would have found a first-class typist, unpaid, a perfect god-send and I told her so. She was inclined to be critical about those. “Surely if a thing is really worthwhile it’ll pay” she said. “I shouldn’t have thought that organizations that haven’t enough margin to pay a secretary can possibly do very much good”.
I am of the same mind as the heroine.
After all, a Non-Profit Organization is, by definition, an organization that makes no profits. Profit is defined as Revenue Minus Expenses, so a Non-Profit Organization is an organization whose revenue matches expenses. That is, they have expenses, and you could and should be part of the expenses.
The Non-Profit Organization you speak at will pay rent, electricity, office supplies, some paid or partly-paid staff members, and so on. It is no part of YOUR business to delve into THEIR finances. Your business is to deal solely with your finances, and that means you get paid each time you leave the office to speak or to engage with a client.