I didn't even had the chance to place an offer  before it was gone.

They tend to care more about an A plus location then the cost per sq ft in rent as they believe the location will drive higher sales.Regional to mom and pop tenants are more sensitive to being in a high end area but not the most expensive center or corner where they feel they have to drive very high sales to have a chance of being profitable.

In the end, I decided to just take the chance and bake it into the rents.  

Based upon forecasting my estimate will be 30-35. 

My estimate is approximately 15k for the addition using subs for everything plus an additional 5-6k in holding costs.

I've found that The Book on Estimating Rehab Costs by @JScott to be fairly relevant in our area.

What is the best way for me to estimate my market value without paying out of pocket right now?

But just know that, if you do, your taxes go down but so do your chances of getting a loan.I have a mortgage broker/friend who refers his clients to me all the time. 

Of coarse a Zillow estimate will never be as accurate as an appraisal however in my experience it is usually within 5%.  

Flipping is all about understanding the math and accurately predicting rehab costs, estimate too low and you lose money, estimate too high and you don't bid enough to get a property under contract.