In your situation, it would be good to get an idea of rent vs pet fees, because if a tenant gets rid of their dogs, their rent would be reduced during the current lease.

She had two questions, which I don't know the answers to, so I'm asking y'all, and whoever knows about this topic, please speak up :)1) If she sells her rental the traditional way, and gets all her money out at once as a lump sum, can she put that money towards paying down the mortgage on her primary residence to reduce the capital gains taxes?

For those homes, so much needed to be done with them that I did not check into low-e or argon gas because at the time I knew that the double pane & vinyl would still be an improvement of energy performance compared to what they had at the time.

I know that the landlord can be considered liable for falls/ slips if/when it was deemed they were negligent in addressing an issue that caused the fall/ trip (ex. knowing of a leaking pipe which caused floor to be wet) However, in this instance where it was due to actions of the tenant, would you initiate interventions to reduce the risk of future falls? 

I would suggest running some numbers to determine if it's even possible, before spending a lot of energy. 

However, as with most aspects of life, fear and uncertainty can almost always  be reduced or eliminated through education and familiarity.

and/or reduce expenses (can you bill back the utilities to the tenants?)

I recommend a home inspector so you can get a 4-Point Inspection and possibly a Wind Mit Certificate - which determine whether the house is insurable and if so, can reduce the cost of insurance.  

I thought the owner might be interested not only due to the energy savings, but also as an alternative to a very costly window replacement and to achieve higher rents.

Example:Duplex purchased for $100,00020% down payment would be $20,000Seller agrees to provide a seller credit of $10,000Your loan amount becomes $110,000 while you down payment reduces to $10,000A conventional loan only allows you to do 2% (maybe 3%) seller credit of the agreed upon price; whereas a commercial loan does not have that restriction.