I am going to disagree or want to clarify @ThomasM125 on one part, however, I don't believe it changes the direct result of your specific question.
- Where I disagree or want clarification, is if you ran a separate business in the building, and materially participated in that business, then the rent would be considered self-charged rental. This would complicate the nature of the rental activity.
- This is due to the fact that rental is by default considered a passive activity.
- Self-rental changes that characterization to nonpassive.
- Based on your facts, while you do own a business within the rental building (your 20% ownership), it doesn't appear based on the limited facts that you or your husband's involvement within your son's business rises to the material participation level. While there is attribution between spouses, I don't see any attribution between parents and children in my quick read of the various regulations.
- If you would be considered material participants in your son's LLC, then 2/3 of the rent of the commercial building would be considered self-rental. If that would be the case, I would recommend meeting with a tax professional to work through the issues and accurate tax filings.
- Ultimately, I agree based on the limited facts, there is no personal usage.
*A reminder that posts in a forum such as this do not constitute tax advice.
Also keep in mind the date of replies, as tax law changes.
