Hypothetically your rich uncle could loan you the money and secure it against the house legally, but he cant be engaged in that activity as a business without the proper license and without following some pretty strict rules.Very few HMLs are licensed to loan to owner occupants. 

Several times I could have secured a property with a 15k deposit on the day (which I had), against a winning bid of 150k on a property less than 15 years old with an MLS and local realtor assessed fmv of over 300k (even the county tax assessor agreed!)

Can I still charge a month's rent for the security deposit? 

Skip the option route, use a purchase agreement and set closing off ten months, you can have delayed settlements for less than a year and you'll be better secured with earnest money going to pay taxes, might consider buying the taxes if you can.

Once the security deposit has been used, you have no leverage.

Debt projects are generally secured loans.  

If there are multiples I let the chosen applicants know the place is theirs, as long as they complete the lease signing process and pay the security deposit, and any other fees needed. 

I foresee finding cash buyers and a title company, that will be fine with closing with assignment, once I do secure a deal as an area of opportunity for me right now. 

You are securing the loan with a building. 

The difference in the type of degree that your grandson will attain versus the one I will have aft we completing my program is job security in the future.