In my area, I'm pretty well limited to houses vs condos, zip codes, and in-vs out of state.

Zip code based or even narrower if possible.  

Know your market, know what a house is worth in the area you are looking in, know the trends in both price and rent for the area.I work primarily in 3 zip codes, I know those areas well (but know of parts of those I won't invest in),,you should know whats going on with the schools, any development planned in the area employment opportunities or potential layoffs,,knowing the area (and of course the knowledge you get from biggerpockets) will help keep you from making a mistake.I look in other areas from time to time, but when I do I have to do a lot more due diligence

What are the best ways to analyze specific zip codes, markets in your area of interest?

I was looking mostly in the 77449 zip code at first, then expanded my search elsewhere.

Since then, I have been making deals but I am scaling back into part time wholesaling for a period of time.Here is my situation:I have a pretty good absentee list of about 700+ absentee owners in several zip codes.

The one trick is that it's a short sale so it needs third party approval.The house is in the Morrell Park section of Baltimore (zip is 21230).

@Grant Glover I am probably as close as I can be without a McKinney zip code.

@Simon Campbell , thanks for the suggestion, great idea :) @Alyn Shek , am new to REI so i am trying to be at this moment very precise of what i am looking (duplex or triplex) and in which area, so right now i wanto learn what is the market in the Bronx, particularly 2 or 3 miles from from my zip code 10462.

All my single-family homes are purchased for the $20k-$25k range and I'm trying to stick to a single zip code in the city of Milwaukee.