A lot of beginners often forget about holding costs (if I'm being honest, I still under-estimate sometimes!)

Property 1:Purchase price - $73,000Mortgage - NONE (Paid Cash)Monthly Rent - $875Monthly Profit - $580Property 2:Purchase price - $65,000Mortgage - NONE (Paid Cash)Monthly Rent - $950Monthly Profit - $750Property 3:Purchase Price - $107,500Mortgage - $80,625 Monthly Rent - $1300Monthly Profit - $435Current Cash Available - $110,000Current Available Equity - $96,500 Cumulative Total - $206,500The available equity was a HELOC loan that was given at 70% LTV so those are real numbers, they would be from property 1 and property 2.The reason im typing this is because I would like to know if there were any builders that could give a rough estimate of building cost per square foot in Kansas City area or suburbs.

Emory-The 70k valuation is a very, very rough estimate. 

From there, form an estimated replacement cost, and write down the estimated remaining life left. 

And an infestation of German roaches that made the pest guy jump (he said).After everything was said and done, we incurred 4 times the cost as I was told/ estimated. 

Consider how long this might take, then double your estimate if you really have no idea.

Advice: Reach out to your lender or someone experienced with streamline refinances who can help advise a more accurate estimate for you. 

Did a contractor provide the $40k rehab estimate?  

So how do the banks estimate OpEx? 

We estimate that we need roughly 9 more properties that generate $300 / month in cash flow to meet this goal.Currently, we are a single-income household.