I think it is far more complicated than simply one number (Rent multiplier, cap rate irr, etc).  

In most cases appraisals for 2-4 units will rely on gross rent multiplier not cap rate.

There are many issues with this line of thinking:Basically, this is a variation of what is known as GRM analysis (Gross Rent Multiplier).

Crowdfunding or it's old school name, raising money from multiple people, becomes a big force multiplier with technologies like the internet and social media.  

And lastly, I reveal there how I made over $37K on a property that other investors would just pass on because they don't know how to make money on a house you buy at 93% of market value.Regarding your goals, I think you should multiply them by 5 or even 10.

Whatever that ratio is I multiply times the current tax bill.

Adding 10-20 units will only multiply your difficulties by 5x-10x.

You are just learning what WILL work and what WILL NOT work.To begin making money multiply the fair market value by either .65, .70, or .80, depending on how competitive your market is.

I have the 11 occupied spots at a value of $115,500 (using the lot rent and a 60 multiplier). 

Utility InformationEnergy Source: ElectricSewer Connected Financial InformationCash OutAnnual Taxes: $8,773Tax Year: 2014Cap Rate (NOI/LP): 7.57Gross Rent Multiplier: 6Total Monthly Income: $8,870Gross Scheduled Income: $106,440Gross Adjusted Income: $95,796Net Operating Income: $47,722Insurance Expenses: $3,400Water/Sewer/Garbage Expenses: $7,833Other Expenses: $28,068Total Expenses: $48,074Total Expenses: $48,074