I started looking at the 40-50k homes but now I'm wondering, since I've had good luck with a 'higher earning' tenants thus far, if I should I focus there. 

Personally, I earn many hundreds of dollars an hour by finding new deals and raising money...

The plan will need to be adopted by a business that would generate some earned income, not just investment returns.

For me, lower leveraging and a little liquidity provide more safety even though I forfeit a little more earning potential.

@Luc BoironThat's flattering, but neither warranted or earned ... no matter how you measure it.Funny thing is I would probably put your father and big brother on my shortlist of those who are "best" at sharing what they do: I've gotten my money's worth out of their highly priced textbook.A list of the most successful would have to include the late David Azrieli, Bob Gaglardi and the Bronfman brothers.My list of "flashiest" - both in their successes and failures - would include the Reichmann brothers (O&Y and Canary Warf ring any bells?).  

I'm a software engineer by day and have always been intrigued by the earning potential of real estate.

Buy where there is a good spread, if we have an oil cycle, then I'll sell high and move my earnings to a more stable market via 1031

If it costs you $0.70 per customer (buying the list, sending the mailer, postage, etc.) then you can expect to spend $700 to earn $10,000 and your net profit without any of your own labor cost is $9,300.  

Instead of marking up 20%, you should be doing [cost]/(1-0.20) to get your price to your customer in order to earn 20% margin.

One of my favorite quotes that my Dad would always tell me was "If it's easy it isn't worth doing" I have always followed that advice UNTIL I read "Rich Dad Poor Dad" and realized that I don't need to work to exhaustion to earn more money.