how do you research a potential farm area?

[Benjamin Barredo]

so I'm reading a book ad the guy is talking about researching cities for virtual wholesaling. he goes two types of comps. He does a am inventory and sales comp for each city and the numbers he comes up with he says "if the cities were the same size" i have no idea how he comes up with comparables if the cities were the singe size. i guess it's similar to comparing homes of different sizes, adding and subtracting where necessary. still, i need a simpler way. what do you all look at when researching investment areas?