Many experienced real estate investors don't advise inflexibility in terms of cash flow. Most say it's okay to tolerate a small negative cash flow but control it under some limit you set for yourself. In many highly sought-after regions, you basically can't possibility find any property with even cash flow. But that doesn't mean you should not invest. You want to project 5 years with negative cash flow, if the total is tolerable, do it.

Every year, the rent will rise, over 4-5 years, your negative cash flow today may be turned into even or positive situation. However, if you are inflexible, you may lose a lot of opportunities today.