You did not underwrite this on any of your offerings though, so you're speaking from direct experience not by observation. 

Additionally, what do you consider the most effective approach for collecting the owed amount?

I have some single family rentals north of you in Delray, happy to share my experiences if you want! 

In my opinion, I would not take the advice you received regarding using OPM is you have no experience in investing in real estate.I would also not look to be a private lender for several reasons1) You are better off putting your money with a corporate bond / CD and get 5-6% with little risk compared to 10% to 12% with much more risk given today's market conditions2) You won't be able to retire getting interest income, which you said is your goal.

If so, what’s your experience been?

What cost-effective options are out there? 

@Kaycie GunnIf you want debt financing hard money or private money lenders will fund with typically 25% down paymentIf you are looking to syndicate and raise money from investors then that is a different animal and you will need to file an sec exemption to raise money and depending on your experience it could be moderately challenging to near impossible.

I am looking for a platform that is cost effective, but allows me to track all the essentials, give owners access, and ease of accounting.

If so, what has your experience been? 

There are some situations where a well-seasoned investor can borrow 100% of the purchase price and come out smelling like a rose, but only because they have the experience and they can absorb the loss if they screw up.Increase earnings.