Check the following:
a. See if the utilities are directly in front of your property. Water, Sewer, electric. I paid $130,000 for water because the fire hydrant I saw was a private hydrant and I couldn't use. Had to run water a quarter mile away.
b. Look around the area and see if new locations are putting in Storm ponds. Took 1/3 acre out.
c. Look and see if they have storm drains $110,000 for mine on 4 acres.
d. We are doing a 4 acre contractor building site. Electric rough estimate is $300,000 to get to panels. And then wire. This does not include the hookup cost at the front of the property, just the buildings.
e. Insulation. $???,??? Spray foam, roof, side walls, etc.
f. Just the driveway for our Self Storage, 7 inch concrete, 25 foot wide by 1700 ft, $450,000. Use this and convert to a sq ft cost for your estimates.
g. Slab will be about the same. A lot more for frost free footings and rebar.
h. Just plumbing for bathrooms and walling off will be $10,000 minimum per unit.
i. Security fence? Would be $40,000 with roll gate, if automated.
j. Exterior lighting?
k. Gutters?
l. Landscaping- see what the development group will require and what you will want, even if engineering fabric with rocks on top. $15,000
m. Engineering costs. Either you will buy a pre-engineered building and still need the site engineered for permitting; or you will pay for both building and site engineering. $50,000
n. Floor drains; no, middle, front outside.
o. Go halfsies on HVAC, they leave if they move out.
p. Same on office space, as O above.
Keep going with your project, but make a spreadsheet and lay out each of these items. Make sure you get hard numbers for the big numbers and softer numbers for the small ones. Key thing is chop this project up and really nail down the big dollars.
If first time out, you might pay an extra 10% for a General contractor.
Start small and Make Your Big Mistakes Early.