Cashflow is a must. Rentals offer such. There are several variables when looking at cashflowing properties that go into generating the cap rate. The key takeaway is that its just one of many tools to compare one property to the next. W/ that said, it's basically your cash return on the deal if you paid cash for the property. One that takes the potential gross income, subtracts out all the potential operating expenses (utilities, mgt, maintence, repairs, vacancy factor, leasing, pest control, taxes, landscaping, cleaning, just to name a few) . The money left over is your profit on that cash investment. Divide the remaining money over your equity and your left with a cap/% return that will allow you to see if you are making a good enough return on ur money and also compare another property/investment. Taking into account your risk tolerance, return expectations, alternative investment opportunities, etc your CAP will very. I hope this helps.