Financial independence from passive rental income: how long does it take?

[Bao Nguyen]

Like many other real estate investor, I seek to buy and hold real estate, and enjoy the cash flow and any possible appreciation.  

However, since my target properties are lower end properties that often requires rehab before I can attract the best tenants at full market rent, I find myself doing a lot of work. The work consists of not just hiring contractors to fix up the properties, but also of a property manager: marketing/vetting for great tenants, repairs, paperwork and tax preparation for my LLC (or researching if I should even use an LLC)..etc. It's a full-blown business - it's not passive income anymore in my opinion. It's work, and it's work on top of my already full-time job. I'm in awe that some own and manage 100+ units.

My question to all of you veterans in this business: what is your income range, and how many hours/week do you work for this income?  If you could start your response with the following 2 pieces of info, it would help me (and a lot of others who think real estate is easy BIG and FAST money after going through their guru-course) :

1) Annual revenue (pre-tax) of under $100k, $100k-$400k, over $400k

2) # of hours/week spent for this income

From my estimates, I would need to own 50+ single family homes, all paid for free and clear, and all rented before I can even start sipping anything on the beach and not worry about finding a full time job to support me in addition to rental income.  Although it's possible to own 50 units fairly fast, to own them out-right with no debt would take many many many years.  Or am I just a failed guru-course student?

...and the problem with taking many years to do this  - 10 to 30yrs in my calculation - is that many low-end properties are already 100+ years old.  How long can a home possibly last?  How much left is left on these homes, where I can pass them onto my kids as an "asset" instead of a crumbling pile of 2x4s?