People tend to think of newsletters as a marketing expense.
(Of course, marketing shouldn't be thought of as an expense at all. It's an investment - at least it is if you do the kind of marketing that allows you to track the results.)
But it is possible to create a customer newsletter that actually makes you money - and not just from the business you get back from it.
A new client of my real estate newsletters business asked today if he could include advertising space in his newsletter.
Of course, the answer was yes.
After all, it makes sense to allow trusted providers of relevant products and services to advertise in your newsletter. It brings income for you, helps reduce your newsletter costs, and assists your readers by informing them of a useful product or service.
If you don't want to do a cash deal, you could always barter an ad in your newsletter for an ad in their newsletter. That would be a great win-win.