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           

Is there a formula that involves multiplying the gross rent?  

Let's say you make mistakes that end up costing you 20% of your property value - both losses are painful, but it will be a lot easier to recover from 1 unit that multiplying it by 20.Also what if you decide the effort is isn't worth the return, unloading the property will be more effort/costly on the bigger property.While you miss out on big upside on a smaller scale, when do you think, you would be more likely to very successful on your very first property or maybe your 3rd or 4th.

Multiply that out to determine how many houses you will need.