I'm considering looking into the option of turning these units into Air B & B's.

This prevents lock outs, and it also reduces your up front cost to re-key a place.

For example, if lightening strikes and the air conditioner gets destroyed as well as the tenant's flat screen TV, my insurance company will replace the AC less the deductible but not their TV, and I'm not responsible in my area for the TV. 

Tenant shall use reasonable efforts to maintain the dwelling unit and any other part of the premises that he occupies in such a condition as to prevent accumulation of moisture and the growth of mold, and to promptly notify Landlord in writing of any moisture accumulation that occurs or of any visible evidence of mold discovered by Tenant.DISCLOSURES: Tenant acknowledges receipt of the following documents: EPA’s A Brief Guide to Mold, Moisture, and Your Home (PDF format may have been emailed instead of actual paper pamphlet)

A roofer is not a consultant and unless they charged a "diagnostic fee" or something like that, which would have needed to be disclosed on the front end, then they don't have any legitimacy to their mechanics lien.However, the fact that it is illegitimate will not prevent the mechanic from filing it. 

@Tyler Jahnke for almost single-handedly exposing what may be one of the biggest scams in the industry today with his "MI case study 2.0" thread, which prevented others from being scammed.

As a Canadian, wants to do air bnb short term rentals, flip long term investments and so on.

I could tell the seller was motivated as he mentioned having several things going on in his life that prevented him from spending time to rehab this property.

The most ridiculous thing they did was placing a charge of $900 on some emergency prevention best practice installations that were never communicated to us directly and clearly overpriced based on the nature of work.

In my condo, it was turnkey except for the air conditioner and I was responsible for everything studs-in.