We know they moved in with a child.

That isn't being smart, that's just being deceitful.Scenario 3 Dishonest, outright lying wholesalerCouple is looking to sell their home, to move to be closer to their daughter and new grand child.

WY master LLC with state specific child LLC or some other structure?

You should check into the impact on any medical assistance to your child. 

There is a small group that gets together in Annapolis run by Joe Child. https://www.meetup.com/RealEst...

They stated there would be 4 persons living in the unit and we have 4 names on the lease, however - how they've added two more adults - an ailing father and a child from maybe another parent they have custody over4.

Our youngest child is 2 and I would predict we have about 23 years of reaching this goal.

Now I had just had a newborn at the time and quitting and betting it all on that career path was not something I wanted to gamble on my family's financial future.

Depends on the state but a parent can transfer by family transfer their primary residence to their child without property tax in California up to a million dollars. 

Property Taxes: Should be safe since you plan on living in the home (because it's a primary residence, should be excempt with parent/child exemption), but you would want to get a second opinion on this.