Along the way, we see so many folks make mistakes that they need to get amended and that can take years to finally recoup all of the money lost from paying to much. 

In our experience, the #1 mistake owners make when selecting a Property Management Company (PMC) is ASSUMING instead of CONFIRMING.It's often a case of not doing enough research, as they don't know what they don't know!

Boots on the ground, or lack thereof, are where the mistakes are made.

@Yooni Choi managing from out of state (OOS) with ZERO previous landlord experience - probably won't go well.You WILL make a lot of mistakes that will cost you money.

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.

Not sure how many PMCs you've had bad experiences with, but we'll take exception to:"Then do a thorough research on tenant applicants (note: leaving this to a PM may be hazardous to your financial health)".BP seems to have more threads about screening mistakes by DIY landlords as opposed to PMCs.Now, if you'd have mentioned Maintenance, you'd get no argument from me:) Even the PMC industry acknowledges maintenance as one of the biggest challenges.Rereading my post, I kinda see how I sounded negative toward PMs.  

The biggest mistake people make is not having enough reserves before going into real estate investments.

We continued in this way for about a year, making steady progress, learning from our mistakes and generally improving overall.

Quote from @Alex Moazeni: You are making the common mistake of allowing a tenant to push you around.This is your property.

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