Any lender should be able to give you a super quick calculation of estimated savings based on those factors to see if this is a good time for you to refi!  

For preliminary numbers analysis, I’m using an online calculator available at this website: https://www.calculator.net/rental-property-calculator.html.

Back of the napkin analysis (or BP calculator) make a conservative offer and see if the seller is willing to play ball.  

When I calculate out the monthly mortgage for a house at this cost assuming a 300,000 downpayment, it would come to around 7450/month so I think 7000/ month is reasonable.  

@Mario MoralesCash-on-cash return measures the amount of cash flow relative to the amount of cash invested in a property investment and is calculated on a pre-tax basis.In theory if your rental income increases by X amount annually due to the rehab while holding your expenses constant so it directly increases your bottom line (cash flow), you can calculate the CoC return by inputting X/$45k (the cost).

Basically if the payment amounts would be calculated like they are being paid over a 30/15/10, etc. year term. 

I use Zillow and the Rental Property calculator on this site to do all of my LTR analysis.

I found that some of their calculations were off when I was looking at certain properties. 

I am currently in contract with a relatively new single family home that looks like might produce some cash flow or at least break even the first year according to the property calculator. 

Please us the Project Submission Calculator onthe site.