This link takes you to “A Few Good Accounting Packages” by Laura S. Quinn and Jay Leslie, an article that contains good accounting advice for small non-profit organizations.
This link takes you to “A Few Good Methods for Processing Credit Cards,” another useful article by the folks at Idealware, a website dedicated to helping nonprofits select software.
The city of Greeley, Colorado, has a facilities rental agreement for the City of Greeley Museums that can be used for a model for yours.