Another thing you pointed out is the timeline of reinvesting this money would be daunting for me at this beginning stage of my learning curve. 

Absolutely no need to over complicate at this stage.

@Ashley Hughes no there's too many free property management apps to justify spending money on a website at this stage.

All of the bad stuff - Not abiding by any rules, smoking in the house, not paying rent, leaving totaled vehicles in the driveway for weeks on end, allowing pets to damage the property, incurring excessive utility bills without compensating for them, all of that good stuff.

At this stage it would just be a waste of money.

Selling costs (realtor, staging, etc.)?

Any recommendations on insurance companies that provide reasonable rates for flips while in the renovation stage?

If you want to compare your findings to Zillow, go right ahead, but do the exercise of searching out truly comparable sold homes so you can learn how the pros do it.You should also be going to as many open houses as you can at this stage in your career, even if you have no intention of buying anything.

I'm still learning, so maybe my confusion is jut because I don't know what causes cost over-runs...On the PB Podcast, I've heard about getting an itemized bit or statement of work, breaking-down labor vs materials, and paying after stages of work are completed, but I haven't heard who's responsible for cost over-runs. 

Lastly, every dollar you pay in excess of your interest goes straight to principle.