Keep your personal safety and that of your tenants and neighbors in mind. 

A landlord does not need to provide a reasonable accommodation for an emotional support animal when:The property is an owner-occupied building with four or fewer unitsThe property is a single-family home sold or rented by the owner without the use of an agentThe emotional support animal poses a risk to the health or safety of other people, or a risk of substantial damage to property (but this risk must be specific to the animal and cannot be based solely on assumptions about the animal’s breed)"Definitely have a chat with a local attorney to ensure your local laws apply, nonetheless since its an owner occupant, it sounds like you have some recourse to deny this request. 

Then armed with this knowledge, when you do hire a PM, you will be able to spot any BS on their part.

Ultimately I am worried about protecting our business's reputation, the safety of our tenants, and having a viable rental. 

Now a landlord (and architect), I wouldn't build out the space without the second stair since it really is a safety issue/liability (especially in case of a fire) if anything were to happen.Full excerpt of building code below:According to the Chicago building code on egress requirements, the third story above grade plane within a dwelling unit [which in this case is the duplex-up unit], all the following conditions must be met:1.) the building is equipped throughout with an automatic sprinkler system2.) the floor area of the story does not exceed 1600 sq ft3.) the dwelling unit has an exit that discharges directly to the exterior at the level of exit discharge.Your third story attic space is unlikely to exceed 1600 sq ft, but you'll probably find the sprinkler system to be cost-prohibitive.

. - ARM's.

Just a small bit of information to arm yourself in regards to the lease and your wife's sister's DTI.

I am risk averse and if I were to purchase, I would tear down to the studs and do a full rehab {this would include getting rid of asbestos shingles and insulation).1) I have done a ton of research and it appears as if getting rid of asbestos is very DIY able assuming you spend money on the safety equipment and use it properly. 

If you have a five year window you should not be doing interest only, ARMs, etc. do a 5 or better a 7 year financing term.  

., but it might make sense especially with Roth IRA or Roth 401k contributions.It gets tricky since you need a bona fide business to business relationship... doing other property management and / or handyman services helps create an arms-length relationship (and rise to Section 162 definition of being a business and not a self-dealing transaction).