If you have a registered nonprofit, like a 501(c)(3), you can often get a substantial break from some SaaS companies.

Some will give you the service for free (rate-limited, probably), while others may not give you a break at all.

I will say Caveat Emptor. If you keep your backend on Someone Else's Machine, they can hold your data hostage. Hosting should be fine, but some SaaS companies have a nasty habit of considering any data they have access to, to be "theirs." May be fine, until they sell the company, at which time, bend over and squeal.

Source: Been doing nonprofit development work since last century.