A common mistake I observe are investors focused on unit count rather than the fundamentals of the underlying real estate that's being bought.

Once in awhile, some internal person makes a mistake and there is a slight delay.The bigger problem is screening S8 tenants to get one that pays THEIR part of the rent on time and takes decent care of the property.We just had eviction court today with a tenant not paying their rent portion AND deliberately causing damages, so their home failed the S8 inspection.

Mistakes will be made, which can cost more time and 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.

The biggest mistake is not truly understanding the exit strategy.

And when you grow too fast (especially in a volatile market like the one we're in) mistakes can get made.

Having hundreds of hours managing a myriad of STRs you really get to learn and get a pulse on what makes a property successful, how to mistake proof a property, and what it takes to keep them performing optimally. 

They then informed me that I could either move forward with the management services, with a nominal discount of $110 for the error, or revert to the Lease Only Option and have the lease transferred to me without any security deposit, as none was collected by the property manager.This mistake has left me in a difficult position.

@Jason EspositoEven with your private Lender being family, is it anything you would do different from your previous deals, any mistakes that you learned, and during your deals besides having lenders that are family, is their anything that you can share that made you successful?

Learn on mistakes.