A clear message from grantmakers today is that grantseekers will be expected to demonstrate in very concrete ways the long-term financial viability of the project to be funded and of the nonprofit organization itself.
It stands to reason that most grantmakers will not want to take on a permanent funding commitment to a particular agency. Rather, funders will want you to prove either that your project is finite (with start-up and ending dates); or that it is capacity-building (that it will contribute to the future self-sufficiency of your agency and/or enable it to expand services that might generate revenue); or that it will make your organization attractive to other funders in the future. Evidence of fiscal sustainability is a highly sought-after characteristic of the successful grant proposal.
It behooves you to be very specific about current and projected funding streams, both earned income and fundraising, and about the base of financial support for your nonprofit. Here is an area where it is important to have backup figures and prognostications at the ready, in case a prospective funder asks for these, even though you are unlikely to include this information in the actual grant proposal. Some grantmakers, of course, will want to know who else will be receiving a copy of this same proposal. You should not be shy about sharing this information with the funder.