Taking it to the next level-buying 3 properties within 3 months

[Chris Bingham]

I want to take it to the next level. I have seen several posts of folks buying several properties (sometimes 10 or more in a year). How is it done? I have acquired 3 properties over the past decade. Each of the properties cash flow very nicely..my monthly cash flow after mortgages and utilities is $3589. I've used some of the cash flow to pay down the mortgages even faster. But I still have over 30K set aside for a down pmt on the next property. I currently have about 190K in equity between all of the properties. I figure I can keep saving and buying a property about once a year, but I'm trying to learn a different way. 

In my mind I can use a portion of the 30K to house hack into the my 4th property, but then if I want to buy another one relatively quickly I will need 20% down for a non owner occupied property...Do I need to get a line of credit on the other properties and use that to buy the 5th and 6th properties? Is there another way to do it? What am I missing here? I feel like there is something I missing when I head of people buying their first property and then suddenly buying 6 or 7 the next year. It doesn't make sense in my mind how they can acquire the properties so fast. If you have acquired properties in fast succession, I would love to hear from you and how you did it. Thanks!