Where did you compile your list, how fresh was it, are you sure it went to a good address?

Assuming you have already done all of the other necessary work and compiled the data you need to pull off a 20k piece mailer, the response alone could bury you and your ability to perform.

Feel free to add me to your list if you are compiling one!

Software programs are getting pretty darn slick at aggregating info that once took eons to compile.

Or if you have a relationship with a CA title company, they will give you an online account where you can compile lists and/or mailing labels for free.

You will see that when you start doing this and compiling information and putting together a list of what is renting or selling for what it will start to make sense to you.

If the comparables in the area prove that a multi unit makes sense, then I compile some similar properties and figure out what was built: Area, materials, number of units etc.

My question is if there ever comes a time when the savings are compiled enough to where it’s no longer necessary to take out this percentage of rent any longer.

I kind of had to overcome my background in finance, compiling metrics till the cows came home.  

You should be doing your own comps to ensure accuracy.That said, we've compiled a directory of these online sites for those of you who want to get a baseline average before getting out there and doing your own DD:http://www.biggerpockets.com/house-value-comps.html