I am kind of new to real estate investing as I got lucky the first two times but now I am looking to invest quite a bit more money and I am slightly terrified. 

Therefore, working with a single real estate agent doesn't make much sense as it will limit you to his/her very limited inventory and he/she might have as main objective to sell a property to you take advantage of your lack of knowledge of the market.

As you progress your bookkeeping business, you'll likely want to learn how to export statements from a variety of property management platforms, as investor books are housed in bank accounts, spreadsheets, and a variety of property management and accounting software!

My name is Nate, and I’m on my 3rd deal as of now.

If you've heard a good podcast or read a good book I'd love a recommendation. 

People always long for the days of yesteryear and idolize the past. 

Is this a person who is, from here, going to turn their life around from the desperate situation that they find themselves in right now, such that they are willing to take a Subject-To deal? 

One place is networking at a Real Estate Investors meeting.

How can a supposedly professional company with an experienced team make such a massive miscalculation?

I had a rental house that burned down.