From Jody Blazek Tax Planning and Compliance for Tax-Exempt Organizations, Fifth Edition:
The type of indebted property subject to the debt-financed rules is best defined by listing those that are not included in the term.
Exempt-Use Property. When substantially al of the actual use of the real, tangible, or intangible property is substantially related to the performance of the organization's charitable, educational, or other exempt functions, the property is not subject to the debt-financed rules. IRC Sec513(b)(1)(A)(i)The exempt purpose usage must occur at least 85 percent or more of the time. Such use must be actually devoted to exempt activity purposes and used directly in the organization's exempt or related activities to be exempt.
I could go on but it's a book. From my church's experience, we rent only to non-profits, 501(c)(3) organizations. And with that, keep in mind that you may be subject to real estate tax. We discovered that not all states or municipalities waive real estate tax on churches or non-profits. Now we are subject to re tax on all the space for which we collect rent. Your state may differ.
Your organization may want to restrict rental to exempt organizations. We thought that our doing so would be all that was needed. As a church, all the Space Sharers (as we call them), do support all of our mission and ministry in their respective missions so we do not have to file a 990T for UBIT and we never rent to for-profit organizations.
Let us know the outcome.