Once you file I would speak with the officer/office person as to how soon you can legally have the locks changed.

If the legal fees is going to be more than collecting 2-3 months worth of back rent, then I don't think its worth it.

Since this real estate business would be owned by my mother and us three boys, I am unsure what legal entity would be best to setup for all of this to achieve the most legal security and tax advantages down the road. 

You have to be clear about roles and responsibilities and know that the BIC should be monitoring your business because they are taking legal responsibility.My recommendation is to visit larger offices and see if they are willing to allow you to open a property management branch under their license.

We share the same legal address, utilities and airways.In this specific living environment with a spouse that has been hospitalized with allergies due to pets, can we decline to accommodate assistance animals in our own home residence?

They can not then legally sign another contract with you.  

If he is going to terminate the lease it has to be before November 1 2018 and after February 1 2018 which was his idea and we agreed on that (in Wisconsin no one wants to move in a blizzard and it’s hard to find new tenants in winter) I have legal documents for a lease, and a blank addendum page to write these details. 

Verifying numbers is pretty straightforward- check tax assessor info for property taxes, get an insurance quote, contact a 3rd party property management company and see what they'd guess as being a realistic rent income, etc.

As for bad tenants, if they pay the rent you just deal with it and see if there's a way to get them out.If they don't pay rent, you go through with the eviction process and just deal with all the hurdles of the LTB.If you can hold the property for 6-12 months without any rent and have a bit of cash set away for incidentals, legal, intentional damage etc... it will never be too big of a deal.

A license will make it legal for you to buy/sell/lease property on behalf of other people for a commission.