Joys and toys in the attic

Do you allow tenants to use finished/semi finished attics for storage?

Some of my properties have trusses and no floor space, but a few have old style framing, and floored attics, where the HVAC and water heaters are.  I have two of them locked to prevent entry.

I have not had an issue yet, but I am buying two houses this week that have finished attics, with pull-down staircases.  My fear is they will 1- fill or overfill it with junk, 2-use it for another living space, or 3- step thru the ceiling causing all kinds of damage.

Any thoughts?