I figured he can't claim as a primary residence as a renter even though that's been his only address for 3 years?

If you claim it as your personal residence, don't also go and try to claim bonus deprecation against it would be my rule of thumb 

If you use Zelle that is probably only going to one of them, so the other person could claim they never received the deposit.

According to the brokerage and agent, these individuals either weren’t serious or claimed they didn’t realize the property was occupied, even though it was clearly stated in the listing.I’m not particularly concerned about the property’s condition or the eviction process, as I’ve already secured some level of cooperation and have basic access to the basement.

THE NEW FLORIDA SQUATTERS LAW WENT INTO EFFECT ON JULY 1, 2024 my Brother was successful with an adverse possession claim in CA.. he was not squatting he owned the property next door and the person who owned it died and I guess had no heirs.

Insurance companies appreciate that evidence if a claim were to be made.  

We've owned this property for 15 years and only once had an issue with a tenant who claimed they weren't informed that it was oil and threatened to sue due to the added expense.

Quote from @Tyler Fremarek: Many people claim you can invest with little or no money.

Video and/or take pictures of everything in case you have to pursue her in small claims.  

Basically, it is clear that this sponsor lost all of their investor's money, and multiple investors claim that the sponsor lost their money, ghosted them, and behaved inappropriately.