Here is my recommendation:1) Secure your financing first; not what online calculators suggest.

They will make you one or you can change the locks and let the tenant know that you secured their place while they were out of town.

It included a clause that said my security deposit from the lease would be applied towards the purchase price, as would XX% of every month's rent payment. 

I received a modification to my original offer on my first deal stating that the current security deposits would need to be transferred to the buyer’s (my) designated holder that “shall be a licensed Georgia real estate broker.”

Private message me.

I want to provide security parking for the tenants.

Usually this is through a down payment from you and a loan from a portfolio lending bank or private loan. 

There are a ton of ways to reduce your costs of maintaining this security barrier like series LLC (assuming your state recognizes them), utilizing lands trusts, limited partnerships, equity stripping, stacking entities, etc.Asset protection is all about setting up barriers or roadblocks in front of the person coming after you.

Many states have limits on security deposit, so any deposit charged would have to comply.

You would be borrowing pre-tax funds and paying loan back with after-tax dollars at 5% that you could invest in tax-deferred environment and grow your wealth at 10%+ rate (there are many opportunities that would allow you to earn at least that such as private lending, syndication, note fund, etc).