If you are targeting markets within a reasonable driving distance, find an investor-friendly agent and ask them to show you what your budget buys in that market. 

It needs more than just laws targeting a few individuals who don't have an RE license.  

As for people call to complain, there are several things to consider.1) Your letter offers no apparent value either in its content, information or the proposition, or2) The caller's emotional state is off and you are the target of the day.Of course, there can be a myriad of other factors however you need to decide if they should, in fact, be eliminated from your marketing or if it might be a temporary situation and you are convinced that what you have to offer us something that they really need and are willing to risk further (and possibly escalated) anger. 

My searches have led me to explore various parts of Indiana, Tennessee, Ohio, North Carolina, and other states - mainly because my criteria is accessible at my target price point in these states (I plan to purchase conventionally).Ultimately, what is the best location for me to hone in on deals? 

Additionally, you could also prevent this "middleman" for potentially targeting another buyer.  

So search areas where comps are 100k and target the dilapidated houses.

If the town where the PO box is at is somewhat small, you could run a facebook ad and target everyone who lives in that town.

Good luck finding a place like this as there is very high demand in Denver.Once you find a location with the correct zoning, if that's the industry you want to target, you're going to have to upgrade electrical to the warehouse.  

If you keep the house 6 months and it becomes self supporting and hits your target as far as cash flow ( you set that goal not just accept what it decides to pay you) than its a win for as long as it's self supporting and cash flowing. 

The marketing campaigns, direct mail, IP targeting, direct phone calls, will all stop in that area and we'll look for another area to develop.