Hey Tyler,  As many have said, recently SOLD sales of similar homes, from within the same "market" as the home you are estimating value. 

Could you do so if it meant saving 60 to 100k as you estimate?

I feel my skill set, with an extensive background in project management, estimating, and renovations, makes me well suited for REI and  I am eager to start taking steps to transition my career to this industry.

In the future, I'd request a "soft pull" from a lender and provide them with your estimated credit score to get a rate quote.

Over estimate the costs and not need them?

If you haven't already, read "The Book on Estimating Rehab Costs" by J.

As @Troy Gandee mentioned use the tax estimator on the County website or call the assessor.

The rents were much lower than I originally estimated, which was a bummer.

The property investment in total is estimated to be 105K with $1600 per month cash flow when complete.

Selling costs would be 8-10% of the sales price but there should be an estimated proceeds sheet that would show you costs.