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.

single or double wide..My exit would be to sell the homes to all the owners and hold the notes till paid off.  10-15 yrs of monthly income is great.  

It is 20" wide.  

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.