The most qualified applicant in my opinion is a family of three, whose credit and background checks are clear. 

Since the property is free and clear, you might consider reaching out to local banks or credit unions, as they often have more flexibility for smaller loans.

sounds like you are on the right track - house hacking or BRRRR to jumpstart the journey is a pretty solid tried and true gameplan

You can do this without a coin-op feature, but then you have to bill the tenants for small amounts which is just one more thing to have to track and follow-up on.

Market rent was about $3,300 at the time, but we agreed to a $5,000/month rent that includes $1,000 rent credit (which was stated on the option contract, not the lease contract). 

Quote from @Tim Casey: Hi there...you're definitely on the right track with your investment strategy.Selling your Atlanta property might be a smart move, especially considering your ARM and the potential for rising interest rates.

HI Stephen,You can always open HELOC or line of credit from your primary house or non primary house, assuming you have sufficient equity and income to qualify.

They allow you to get funds at more favorable terms than with a loan or credit card.

Do I write the LLC a W-9 and write a check from the LLC into a personal account for tracking purposes? 

I put my criteria clearly in the listing: 3x income over rent, 85% on-time payment history on credit report, and good references from past landlord.The biggest mistake you can make is taking the word of a current landlord.