I would have to disagree with staying away from the Outer East Side. A lot of it may be full of troublemakers, and I would never buy a class C/D property in a class C/D area but the reality is there still decent sized pockets of good hard-working middle-income people. The trick for me has been finding a class C/D property within those class A/B pockets and bringing it up to or just above the standard within that area. Then charge slightly less than market and over screen. There is plenty of money to be made in that type of value add game.
The last set I bought increased in value over 50% in one year and market rents are up 20-30% in under 18 months. Thats not including the under market rents I bought it with, which is what my offer was based on. A portion of those increases are simply market factors, but its also being driven by people moving out further after being priced out of the "more desireable" areas.
On second thought, I agree, stay west of 122nd, its nothing but trouble out here.