Take these if you take nothing else. We ask some version of all four on a first call, and between them they settle most cases inside half an hour.
One. Is the workflow genuinely yours, or just familiar? There's a real difference between a process nobody else could run and one you've simply run this way for eleven years. Both feel identical from the inside. The test is whether you can explain to an outsider why the difference matters to the people you serve — not to the people who work there.
Two. Is it central to the mission, or adjacent to it? Software that delivers your programs is a different proposition from software that administers them. If the thing you're describing is how your beneficiaries actually receive what you do, custom software is a much easier argument. If it's bookkeeping, scheduling or email, it's a much harder one.
Three. Can you name what breaks if you don't? Not "it would be better" — what specifically fails, and when. A grant report you can't produce. A waiting list you can't see. A compliance requirement you meet by hand now and won't at twice the volume. If nothing on that list is concrete, custom software isn't this year's purchase.
Four. Who owns it in year three? Someone inside your organization has to hold the product after we've gone — deciding what gets built next, arbitrating between departments, saying no. They needn't be technical, but they must exist and have the authority. If you can't name them, fix that first.