My goal is to do a full 20, get out at 42 years old, and be done working with enough money to cover expenses + have ~$10K/month excess.

@Cherrell Thomas cash flow is the profit that's left after debt service, property taxes, property management, common utilities (if any), reserves for repairs (small things like leaky faucets, AC servicing, etc), and capital expenditures or capEx (larger things like a new roof,new HVAC, major plumbing overhaul...these are treated differently on taxes, written off over a specified longer period) and other expenses.The first item I mentioned, debt service, is where the answer to your question is.

In CA HOA's can be through the roof and really cut into your bottom line. 

This is where I live - my 3 apartments cover my mortgage and I am in essence living here “for free.”

@Josue Velney That doesnt sound unreasonable at all . 10% gets you on the schedule , covers the paperwork time and phone call time to get the job up and going .  

Rest looks fine,Key is roof, water heater, appliance, plumbing etc.

I need to replace the roof on my house.

Thanks in advance for your feedback/ If it is the old style 1/2" thick oak, and you have enough to cover a couple of rooms, yes, you can probably find a buyer.

Any major problem (roof, basement, conditioner, driveway, tenant turnover, etc) may cost 5K. 

For the first few years, I barely covered the mortgage with rent, but now I get $2400/month (and recently refinanced to a $1,791 mortgage payment) which is better than it used to be.