BUT I still own 50 other income producing assets with high(ish) equity.

property is worth 100k and rental income is 1k. does that mean that two units are producing $500 each?

I wouldn't eliminate an income producing rental unit until I knew for sure.

As my military commitment has yet to be for filled, one of my short term goals is to purchase enough properties that produces horizontal income that will replace my vertical income [BP podcast 190]. and get a jump start on my life after retirement.  

While the plant grows, you take great care to water and weed so the plant will do its best.Suppose that one plant only produced one ear of corn.

I appreciated those parties that gave me some numbers to work with, and I also appreciated the general council that direct marketing this property to cash buyer investors via direct mail, is unlikely to produce good results.I have a local real estate agent who has been VERY interested in marketing the property, who is allegedly a top seller in his organization with Keller Williams Realty.

I have lived in Nashville, TN since 2004 making music as a record producer, engineer, and mixer.

Think how much more profit you could produce if you could find those off market leads for rental properties you wanted to hold.Do a bunch of reading here on BP about marketing and wholesaling, especially marketing for leads.My favorite book for rentals is Milt Tanzer's Real Estate Investments and How to Make Them, on Amazon.  

If you do make each letter customized with names/addresses is there any good tools/sites out there to mass produce these? 

I have seen some dumps that actually chip branches, and local residents can get the mulch produced for free or cheap.