Buying items via MLM is no more immoral than buying a used car through a dealer. It's the abuses of that method that are well known, much like the sleezyness of the prototypical used car salesman. But there are actual good MLM salespeople as well as used car salesmen. The method itself is not immoral (It's not gambling) just some of the practitioners.

That being said every single printed congregational directory I've seen has a statement "For Church Use Only - Do not copy without permission from your local church leaders. Not to be Used for Any Commercial, Business, or Political Purpose" - So there is a strongly worded statement about using church resources for your business.

Or perhaps you were looking for this - https://www.mormonnewsroom.org/additional-resource/personal-...