The former use as a auto repair could present some concerns and you should find out how the former heating oil tank was abandoned (removed, closed in place, etc). since you are converting this building as opposed to demo so you wont be excavating impacted soil, the principal concern would be potential for vapor intrusion since you're planning on converting to residential. this can be addressed with a system similar to radon system.

This is far less costly, since this is far less intrusive.

They can be intrusive so best to be on your best behavior.

Like the kind of bad that made me suspect there was probably some water intrusion in the attic and walls. 

I agree with Greg make sure you get an inspection with a reputable inspector, some even will allow you to walk the property with them non intrusively (while some find it annoying because buyers ask lots of questions) and for sure get and estoppel agreement from the seller as well to validate you COC return some renters haven't paid rent in months.

If she wants $12 for ruined food, I'd pop her a $50 gift card from the local grocery store, and just let her pay the rent.The interior rat intrusion must be stopped, they carry diseases, like plague and dysentery.Good Luck!

Having said that - we own our own 2 places and do everything ourselves, including cleaning and repairs, and I doubt we have more than 5 hrs a week put towards them.Get involved with your guests without being intrusive...I ask them to message or text me when they arrive (I want them to say in writing that the place is ok).

A property we have under contract had a sewer scope that came back with severe root intrusions, and the inspection company recommended that the sewer lines be cleaned out and rescoped.  

I tell prospects I am not set up for section 8 and have no intention of adding another level of government intrusion into my business.

If you say "inspection" it sounds more intrusive to the tenant than "seasonal maintenance".