own 9 rental properties, what should i do next?

[Ryan McCook]

Over the last 5 years, I have acquired 9 rental properties in Phoenix, AZ. Homes cash flow approx. $450 per month each (some more, some less), and there's quite a bit of equity now since the market has risen. Amount owed, approx 1.3 m and they are worth approx 2.2 m. I don't have much liquid cash to keep acquiring. I can go the slow route and pick up maybe 1 home a year, or I could consider cash out refi and pick up another 9 or so properties, but the margins on my existing 9 would probably just cover maintenance and rent loss if i cashed out. What would you do in this scenario? I have tried my hand at flipping, but not with significant success. My first 2 homes netted me about 8k total.