Selling a rental with tenants in place (Tampa, FL). How do I verify Proof of Funds to avoid wholesalers?

With the insurance premiums in Florida going absolutely insane lately, I'm looking to offload one of my SFR (single-family rentals) in Tampa. It’s barely cash flowing anymore.

The issue is, I have good tenants in there and I really don't want to disturb them with a million showings or put a sign in the yard. So I'm looking at the off-market route.

I’ve been talking to a few local buying groups. One of them, Home Options, gave me a verbal offer that is actually close to what I need, but I am terrified of getting tied up in a contract with a wholesaler who doesn't actually have the cash and just wants to assign the contract.

For the pros here: What is a "reasonable" Earnest Money Deposit (EMD) to ask for to weed out the fake buyers? Is $5k enough?

How do you verify their Proof of Funds? Do you call their bank directly?

I just want a clean exit without screwing over my tenants or having the deal fall through 3 days before closing.