why would investors choose COC vs ROI vs passive income?

[Ashley C.]

Just now reading through the PDF for Podcast 200: "A Step By Step Guide to Buying Your First Real Estate Investment." Under #6 Set Your Goals, I found "...How do you see your real estate portfolio looking. What are the quantifiers you need to hit to have a "successful" property. Do you want a certain cash on cash return, or a certain ROI, or a certain amount of passive income each month. Figure out what you want."

I understand cash flow as passive income to replace a 9-5 job, but I don't yet see how COC or ROI can be used to my advantage. I'm sure there's a combination of life stage, where you are in your investment career, tolerance of risk, growth vs. asset protection. Any insight would be great. If you have any recommendations for RE finance/math books that'd be fantastic. I have a lot of learning to do!