How to prepare an affidavit of not renting our commercial swimming pool to the public and not selling food to the public which I need to issue to the Health Department.?

When you talk to a lawyer (which it sounds like you should definitely do), use the Word "affidavit." And "commercial." You might be able to find some kind of free advice if you look around (various media and social assistance organizations are providing this service nowadays), but if not, a single consultation with an attorney shouldn't be too expensive, and should be sufficient to take care of this problem.