In the USA, I have noticed that holding a children's aikido program -- 1-3 classes per week, 1-1/2 hr classes after school and a saturday morning class -- often makes the difference. Kids bring in a cash influx, and often their parents will join, or their older siblings. Being tied to a park district or school extracurricular activities program is a plus, too. Having a kids class is great advertising for the adult programs, too; somehow, the ability and patience to teach kids seems to add a positive spin to a dojo's reputation.
My old dojo might have folded, financially, if not for the kids programs and the dedication of the few senior students willing to teach it.
Of course, it helps to be placed in a suburban shopping district, too.