I think if you understand the price per unit as well as the price per square foot in the zip code and nearby zip codes that will give you a good idea of the comparable market analysis approach and appraiser might use.

Be sure to review property tax statements and verify any zoning or code compliance documentation.

We live in a very intersting, diverse, and complicated market and understanding the intricacies is very important - especially for a new investor.Markets in the same zip code even have their own submarket and tendancies depending on location and its important to look at things hyperlocally in philly.

Example: I define what zip codes (or neighborhoods) that I buy in.

What ghetto city/zip code in AR did you find 2% rule? 

Just for your own sake I would pick just a few zip codes to focus in on first and committ to reviewing/analyzing 50-75 properties on those zip codes.

This months zip codes all produced an ROI of 7%! 

You need his rank, time in service (you can even guess really, doesn’t vary a ton), and zip code.

But that doesn't seem like a good idea to me and would probably not be to code. 

For the modifications, cities generally focus on safety and code compliance, but since you're considering structural changes like wall removal and garage conversions, obtaining permits is key.