The first mistake is the property is free and clear.  

@Jordan Miller most Class A & B rental properties bought since 2021 really don't cashflow from day one.Class B will take 1-3 years to start showing cashflow.Class A, 3-5 years.Current investors keep making the mistake of looking back at deals from 5-10 years ago when prices & interest rates were both a lot lower, but NOT rental rates.

It sounds like mistakes were made on the properties but I'm also questioning the market (you didn't say where these are). 

This is going to take years and years of learning and mistakes.

However, chances of making a mistake or overlooking an opportunity to save are higher when it comes to rentals.The dilemma is whether it's worth paying a professional in this case.

But, I was once a paid preparer and prepared or supervised the preparation of tens of thousands of tax returns and I saw some pretty stupid self prepared mistakes.

I think too many REI focus on either CF or equity, which is a mistake. 

And finally, What are some common mistakes new real estate investors make, and how can I avoid them?

You can hear real-world examples of how others have built their investment portfolio and (hopefully) learn to avoid their mistakes.4.

You can hear real-world examples of how others have built their investment portfolio and (hopefully) learn to avoid their mistakes.4.