What is the sq footage of the storage facilities within 3 miles of this property.  70 units is pretty small.  

It is not based on square footage it is based on bedrooms.  

Hi Wendy, If you can add living square footage, it will definitely add value; just make sure it is all permitted.

@Chad McMahan the comps that I was looking at were all in the same or neighboring area with close to the same beds/baths, square footage, etc.

Pictures, receipts, square footage.  

Address:Westcliffe Ave, Richmond, VA 23222Type: HouseBeds/Baths: 4/2.0Square Footage: 1,514Year Built: 1945Lot Size: 4,356 sq. ft.** Purchase & Rehab **Purchase Price: $115,000 ($76/sq. ft.)Purchase Costs: $3,450Rehab Costs: $7,500Down Payment: $28,750Total Cash Needed: $39,700** Financing **Loan Type: AmortizingLoan Amount: $86,250Loan to Value: 75%Loan Term: 15 YearsInterest Rate: 4.5%Monthly Payment: $660** Cash Flow (Monthly) **Rent: $1,260Vacancy: -$126 (10%)Expenses: -$504 (44.4%)NOI: $630Mortgage Payment: -$660Cash Flow: -$30** Returns & Ratios **Cap Rate: 6.6%Cash on Cash: -0.9%Return on Investment: -3.9%Return on Equity: -0.9%Internal Rate of Return: -3.9%Rent to Value: 1.1%Gross Rent Multiplier: 7.6Debt Coverage Ratio: 1

You could enclose the front half, and leave the back open as a covered patio/Enclosing part of it would also add to the sq footage, so you may get some money out of it as well. 

Maybe a price per square foot or some sort of factor I can multiply by the difference in square footage.

I'm not a RE Pro, but the most potential seems to be in adding a bed and/or bath within the existing square footage. 

What bed/bath counts are the units and rough square footage?