My inherited tenants ALL SMOKE and none had security deposits. 

If it's a wholesale deal then once you find the end buyer, their funds would cover the initial deposit.

You can deduct that amount from the deposit and refund the remainder.

It's only been a week, but what are my options if they do not return and the RV just sits in the slot? 

If you’re concerned about the cash income, you could consider additional safeguards, like a higher security deposit or using a guarantor.

These self employed 2nd mtg's are typically based on alternative method of caluclation like profit and loss statements if you're self employed or the last 12 months of bank statement deposits using a formula to derive an income from these deposits (like 50% of all annual rolling 12 calendar month deposits X 50% /12 months = monthly income).

They stopped making the monthly interest payment ever since June 2024 and are being investigated on charges of Ponzi Scam and are not releasing investors original deposit.

The thing I like best is the interest is deposited in my  account every month.

Worst case deposit money at each bank and earn.  

At a bare bones minimum, the letter confirms the start/end dates of the lease, monthly rent, paid-through date, absence of any prepaid rent other than the current month, and security deposit amount.Better, it will include statements there are no unresolved claims or disputes or repair issues with the current landlord, and no verbal or written side agreements.Better yet, it will include a copy of the tenant's lease, and a confirmation the lease is a true and correct copy with no amendments.