The biggest mistake is not truly understanding the exit strategy.

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. 

@Martin Yip Toll So You are making a mistake treating your debt relationships as strictly transactions.

BiggerPockets is a guru at what it does for BiggerPockets and it's free to chat and explore new ideas and relationships.  10K is a drop in the bucket if you have the desire and will to make that turn into 500k, so don't get twisted as passive income you will not work for and make mistakes.People charge 10k for single-family wholesaling I have looked at many programs as I didn't know where to start and think of the mistake I would have made if I bought the wholesaling program. 

We've made mistakes as well.

This is an all-too-common mistake: a rental sits vacant, less-than-desirable tenants are approved, and then those tenants don't pay and cause issues.You have to rip the bandaid off and ask them to leave.This may sound harsh, but it's not entirely the tenant's fault.

@Ashish Wa you always end up getting exactly what you paid for.You should only go cheap when YOU know exactly what you are doing.Newbies trying to save pennies, almost always cost themselves dollars via their mistakes.