The husband stayed back and has subleased/allowed his daugther and son in law and 2 kids to move in without my consent.

With the tenants consent, you can pull their credit history.

SituationFirst, my tenants decided to make alterations to the property which they are clearly not allowed to perform without the landlords consent per their lease.

SituationFirst, my tenants decided to make alterations to the property which they are clearly not allowed to perform without the landlords consent per their lease.

I do not know this person and have never consented to her occupancy of the home.

The remediation costs were in the six figures...There shouldn’t be anything illegal about doing work to the other party’s property with their consent.

If B holds title subject to just the seller financing, can you JV with B, have B transfer title to the JV subject to the seller financing (with A consenting to this) and then just have D GC the project? 

Since you don't own the property you cannot make any major repairs or improvements to the property without the owner's consent because if you make repairs and don't pay the contractor(s) then the contractors will file a Mechanics Lien against the property and the owner will be liable to pay the contractors.If you do repairs to the property and you don't own the property the owner can sue you for destroying the property.Should the seller decide he (or she) no longer wants to sell the property because he either wants to keep it, or he can sell it for cash on the market then he will sue you in court for whatever his attorney can come up with and you can get sued just because the contract the seller wrote has some b.s. that makes in not valid.It doesn't matter whether you are right or wrong when  you get sued because when you receive a Sheriff serves you with a lawsuit you now have to make some serious and hard decisions in regards to whether or not you want to pay an attorney $50,000 to $100,000 to settle the lawsuit that often takes up to 5 years to settle in court.How do I know all this?

Some people describe this as who pays the commission, hosts or guests, but as long as you understand before setting rates, it does not matter.VRBO charges higher commission (but again you can compensate for that by set the rates differently.)AirBNB will refund guest without your consent, and can be very inconsistent in doing so, depending on what agent answered the phone.

He is unable to transfer the asset while they have an impending divorce so unfortunately there's no legal way for him to convey the property without her consent.