Rental Property Empire?

[Michael Lewis]

Feeling a bit frustrated. Looking for inspiration. I currently own 6 SFR's and under contract on #7. I buy to hold and always felt that eventually with enough property I'd start to see real passive income. However with 7 properties I expect to net $2,700/month(with no maintenance). I run numbers before each deal so I account for the expected expenses however I'm starting to see that my portfolio really only takes care of itself and doesn't do much to bring in real passive income. Allow me to elaborate. There always seems to be unexpected issues that arise with rental property. If it's not the tenant it's the property. When it's time to see what these properties net each month it's always less because of one thing or another. Maintenance, the tenant is short rent, the water meter is broken, etc. When I had 1 or 2 properties and an unforeseen issue would arise for $500-$1,000 I'd lose my mind. I'd get so upset. This would bring me negative and I'd be out of pocket. What kind of investment is that right? Now with 7 properties I find that when these same issues arise the cost is simply eaten from the cash flow coming from the other properties so I'm not personally coming of pocket so to speak. The question is however, how can a rental property investor build a portfolio that both takes care of itself and nets 8-10k/month of passive income? What does it take? 30,40,50 properties? Is the ticket to switch to MF? I'm an OOS investor and multi-family is a bit daunting. I'm not a big fan of syndication as I believe it's far more advantageous to the syndicator. Also, they are short term and I'm looking for long term. Buy and hold forever. I've hit a wall as I'm beginning to feel like there is no reasonable way to win in this game yet RE is the most tried and true form of investing for long term wealth right? So, what am I doing wrong? I'd appreciate some insight.