You have to have a fairly large scale to justify it.

Someone needs to take the reservations, communicate with guests, and keep the calendar updated.

Can you use the local fair market rent amounts to determine a good rental amount to charge?

Therefore, it is a fair expectation that you ask the seller.

This is very surprising to me that an email to them went unanswered - please forward you communication to [email protected] to me ([email protected]) so that we can get to the bottom of this. 

BUT....bearing in mind Andrew's original caution about the "lesser of the two number's" you could still get all your money back out of the deal fairly soon no?? 

I already own 25 units so I know the market fairly well.My plan has been to acquire a couple (or three) 4 plex units that should net me $150 to $175/unit/mo (based on what I have seen over the last 3 years with my other units).

start fully documenting everything and take lots of pictures, I would start communicating via email or by letter, even send them a certified letter stating damages etc, sounds like you didn't hire a qualified roofer. send a copy of everything to your attorney maybe even have him draft a letter demanding a response, if push for a refund + damages and go with a new roofer

To qualify for rent on the property you are purchasing, the appraiser will do a rent schedule to determine fair market rents for qualification.

fair is fair.