What Cap rate do buyers look for

I have been reading “How to make Big Money in Small Apartments” by Lance A. Edward and foreword by Ron Legrand. I am pumped to buy small 5+ unit buildings. It seems to me that unless you buy buildings with a minimum cap rate of 20%, it is hard to make it work. I am going with the assumption that the buyer is financing the property of course. My goal is to net $100/month/unit AFTER expenses, financing, vacancy, repairs, etc.