It's fairly common something has to give in this, we don't usually get all 3 to be ideal.

It's pretty common to find 2x more rental units available than homes for sale.   

I would mitigate through trial and error and as much common sense as possible. 

Common fees will include a set-up fee, a leasing fee for each turnover or a lease renewal fee, marking up maintenance, retaining late fees, and more.

This is actually the more common situation, in my experience.After signing but before the deed was recorded, the seller got scared that the buyer was a fraud, was not going to pay the mortgage and was simply going to rip the rents (as @Jay Hinrichs likes to say) and torpedoed his own deal by alerting the lender of the transfer!

I'm getting ready to tackle my very first BRRRR and I wanted to see if the community could share some common mistakes to avoid?

Is 20 year ground contact lumber common?

@Femi Ibrahim unfortunately stories like yours will only get more common in the next couple years.

A common serious issue would be no heat in winter time.

Your story of "bad" financials that banks laugh at is all too common.