So the title is overly simplified in that obviously no one can answer that question in the abstract for someone else.  But, how would YOU go about determining the answer for yourself?  What metric would you use to roughly calculate your anticipated cash flow from future equity invested?  

Perhaps look at this via a hypothetical situation (not my own circumstances).  Maybe you're about to get an inheritance that you believe will leave you with x$ in cash to buy real estate with and you want to figure out if it will make enough monthly cash flow for you or your spouse to quit your day job.  What back-of-the-napkin numbers would you apply to estimate what your cash flow expectations should be once you've invested the funds (knowing what you know about what you can accomplish in the market once you have the funds in hand)?  Similarly, perhaps you're busy building equity in your current portfolio and are fantasizing about what that equity would have to reach in order to restructure the portfolio to maximize cash flow to enable you to quit your day job and invest full-time.  What assumptions do you make in trying to pencil that out?

I'm fully aware that there are tons of variables (the use of financing or not and the terms thereof, the property type, investment strategy, etc.) - my point is to cut through all of that assuming that you know what you would do with the funds and can estimate what your expectations would be based on your experience.

Thanks for playing!