From the
UEFA Club Licensing and Financial Fair Play Regulations, version released on 1 June 2018 (which is the latest version I get from UEFA's website).
Annex X details what does and doesn't count as income, and by virtue of Section A, paras f) and l), income from "non-football operations not related to the club" are excluded but those related to the club are permissible.
As to what this means, the following is from para l) of Section B of Annex X of the Regulations:
My understanding has always been that rent from facilities located on land around the stadium owned by the MCFC JV with the City Council, including the collar site in the fullness of time but also Co-op Live, can be included by virtue of the first bullet above. Happy to be shown to be wrong if I am.