He just said "now I don't feel appreciated, let's settle those favors I did you before we proceed any further" and sent me an invoice for $2K for the lost materials + time with the break-ins.Overall, the job seems to be ~80% complete but with poor quality, and I will absolutely need to hire someone else to fix his mistakes.

I recommend using an experienced agent to help you buy especially off-market deals to help avoid costly mistakes.  

Anyone have an idea of whether this is a mistake in the book or my/Google's calculations?

You made a mistake in the very beginning by unclogging the toilet. 

This is the biggest mistake we have ever made.

The biggest mistake that I see out of state investors make is unnowingly buying in the wrong neighborhoods and buying the wrong asset class.

Although its not the same as starting a syndication it can be at a lot smaller scale which can be more forgiving for mistakes.

It's a dual weapon.There's even a big net cap/cash flow poster on here that's more or less walked into this debate and admitted not holding was a mistake.

@Ankush R.Recommend exploring as many sources as possible to get referrals AND cross-reference them to get as much accurate information as possible.Check out NARPM.com, BP’s Property Manager Finder (BiggerPockets: The Real Estate Investing Social Network), etc.Also, encourage you to learn from the mistakes of others - by reading posts here on BiggerPockets about owners not having their expectations met by their current Property Management Company.

I'm looking to avoid rookie pitfalls/mistakes/regrets.