The people who buy multis know how to evaluate, negotiate, and put under contract, so you'd have to be very very good to get a deal for them with margin in it for you.... probably not the best thing to bet on without more experience.Oh, and that deal I lost money on?  

To add to what Jon said, you might be able to bet on LUCK to keep your expenses down if you're only going to own one duplex.

Used older house doesn't need a new a/c or a new stove, fridge etc.

I don't bet on appreciation.

That said, there are even more people projected to move here than there are projected new housing units  - in all likelihood rents will continue to rise and prices will continue to increase.That said, it's a risky proposition to bet on continued growth - a hiccup could cost you significantly.  

I welcome BPers who live in the burbs to provide some real numbers to my estimates here.Your bet on the King of Prussia area is way off.King of Prussia is in Upper Merion Township, and that township has no earned income tax - see link:http://www.umtownship.org/index.aspx?

What area do you want to focus - A, B, C or D areas. 

If you feel lucky, go to Vegas and bet on red on roulette.  

It might be less cash flow than linden or other c or d areas in columbus, but almost every deal is better than the 1% rule and if you purchase right there is a lot of opportunity to buy low and sell high.

I have too often seen vendors giving widely inflated classifications to properties, such as B+ to what is only a very average house - C or C+ at best.