This was a 1031 exchange so the deposit was with 1031 money and financed the remaining balance with a 10 year fixed loan.

The previous landlord stated there was no deposit, and the tenant's signed lease states there is no deposit either.

Now, we haven't signed any official paperwork nor finished the walk-through yet,  I still keep his deposit, he move his stuffs out already, but he doesn't let me charge this month rent to this deposit. 

The existing owner needs to put up a non-refundable deposit (of about 10%) and will move out the day you close on the resell by a definite date. 

However, one taught I have been contemplating, is a lease-option; wherein, I would deposit US$9,000 as option fee, and make monthly payments of US$5000 per month for 60 months, then refinance balance of US$600,000 from the bank or private lender after analyzing the long-term earning potential as a villa.

Like a higher security deposit and/or a cut of the net profits. 

See below for information directly from seller:"2 BR / 1 BAOn a Lease/Purchase Contract for $45,000Tenants paid a down payment of $1350, Leaving a balance of $43,650Contract is at 180 months at 10.6% on $43,650 = $485.22/moThe Buyers are paying $112/week and usually pay every two weeks at $224, deposited into my bank account.As of now, the balance of the contract is $35,300.If, the Buyers pay the remaining 117 months, the total remaining is $56,770.74The Buyers love the location and the house for it is next door to the wife's parents and want to stay and finish the purchase.There is however some damage to the house of $7800, Quoted by ******.

You may also want to include a separate page with instructions for leaving the home clean and offering to refund their deposit within five days or something. 

Then they would complain to me how it was "unfair" I charged a late fee because the 3rd fell on a Sunday, so they couldn't go to their bank (or deposit at my bank). 

The tenant has a bankruptcy and I took a chance on them with a higher rent + double the deposit.