Aloha,At a minimum create an addendum to add/remove the relatives to the Rental Agreement at each change, and copy ID/Passports to confirm identities.

I'm also not sure why the husband thinks he's entitled to a cut of the profits, unless he's paying an identical cut of the expenses.  

I spoke with him briefly and he sent over some initial documents but I was skeptical of the process and giving out my personal information due to me having a good score and the potential for identity fraud.

@Aaron Trommater My expense estimates are nearly identical to yours. 

And unless your rental agreement is identical to the owner before you, that's probably a necessary thing.  

The location of the fourplex is located on a dead end street with about 20 of identical fourplexs’  on both sides of the street, which seems odd to me .

I was surprised and disappointed to see that all of the numbers for these properties (occupancy, average daily rate, etc.) were identical in both datasets.

That could mean unlicensed people abroad answering the phones, not protecting tenants info, that could make you liable for identity theft. 

The form is tricky, has bunch of codes to show that its not a sale but just an identity change.

A nearby almost identical property to it grosses $130k.