Hi Charles, sounds great, but Emilio and I are thinking the same thing, that's really high. I did 6 plats and 5 houses and the whole zonning and permit side wes less than a grand!
Maybe you can do some of that yourself. I re-plated the existing simply by writing new legal descriptions and the drawing had to have the measurements (to the legal) and is not to scale. A hearing and an excuse to do it was all that was required. Since it's an existing lot, seems a minor subdivision would fix it for you.
You have a good plan working. As mentioned above, oversized lots with existing homes appraise at ther lot value for the lot required, the excess is usually a third of the value per sq ft since excess or additional land is a small bonus, but when there is enough to subdivide another legal lot, you can get a steal of a deal!
Jennifer has it down! But I don't see how a couple of duplexes can pay for streets, curbs and gutters, here that runs about 100 bucks a foot and a cul-de-sac a little more. FInding existing properties with excess land along the street is worth looking for. Good luck, Bill