Finding Property Value of Generated Leads

[Gabriel A.]

So I'm doing tons of research and gathering different lists of properties I'm going to target during my Marketing Campaign. My next step is going to be getting phone numbers. 

When I begin my direct mail marketing campaign how exactly do I know whether the houses I'm targeting are worth 60k or 400k?

The range I'm looking for is between 50k-100k. I just realized I could be sending mail or spending time on the phone or potentially meeting up with people when their homes are completely out of my range.