;) I bet the Bel-Air mansion is also in the name of a trust or LLC, and I bet it is in a different name than any other properties they may own ... rich and famous quickly learn how to become rich and anonymous, but the truly smart rich folks never seek out fame in the first place ...

I would have the ducts cleaned, furnace/AC system cleaned as much as possible, change the filter, and then run an ozone machine with fans set up to circulate the air for 48 hours.

If I could add to what John Leavelle said  ; it could cost as much as $60,000 to do a full Rehab here in the Philadelphia Area        My Friend Sean just did a Rehab in the Port Richmond Area Close to Fishtown and he it was $60,000        Sean has done many flips and I thought he went as "Budget" as you possibly can , for an example ; he paid $7,000 for a brand new HVAC  (Heat & Air Conditioning)  with new duct work , where that would have been double in the open retail market       Good luck with the project & feel free to reach out to me if you need any help or have questions SincerelyRick      

Do they use mini splits or forced air?

I have 1650 sq ft under r air and 2050 sq ft all together. 3/2 with a mother in law suite.

Time to find a Air BnB!

Air handler, furnace, condenser.Total bid for all work was $32500.

I’m interested in collecting “ground rent” with little to no tenant complaints ever … no trouble calls about leaky roofs or plugged up toilets or air conditioners that go out on the hottest day of the year.If the only real value here is that of the rental cash flow, what’s this thing worth?

I've been so up in the air with reading all the pros and cons, I especially worry about people saying to beware since agents can be open to lawsuits when buying investment and representing themselves. 

We took it one step further and swapped all of our multifamily to electric air handlers as well.