Have you considered the cost of the options? Frac the 300 foot deep well and hope it increases yield? Trench a line to the well that has iron and install an iron filter? Drill a new well and hope it is free of iron and has good recovery?
In my area, most of the mud wells (cased to bedrock) have lots of hardness, iron, and manganese that need remediation with equipment that require constant maintenance. Most of the deep (rock bore) wells produce better water albeit, sometimes not as plentiful. My neighbor paid $48 per foot to drill 300 feet and then had to frac to get enough yield. It is a crapshoot. Drillers are willing to go as deep as your bank account can afford and offer no guarantee.
You say try to sell a place that has a storage tank. I say try to sell a place that has poor quality water with perhaps a crapload of water conditioning equipment.