Utility infrastructure is either 250k or 900k depending on who I ask

Spend the 25k. You are trying to resolve an 850k spread and the extension costs 3 percent of the spread, and it applies to purchase if you close, so the real cost of the option is only lost if you walk.

But spend it on the right things. Two calls should happen Monday. First, the electric utility's commercial service planner, not the customer service line. Give them the existing service size and the proposed connected load and ask for a preliminary service study. They will tell you whether the transformer and primary can carry it and what their contribution policy is, which is usually a formula based on projected revenue from the added load. That answer alone collapses half your range and it is often free.

Second, the state agency that permits the treatment plant. Ask for the compliance history on that permit. Violations, notices, sampling exceedances. A plant at the end of design life that has never had a violation is a different risk than one with three notices in five years, and the file is generally public record.

On the pedestal number, 2,800 each is plausible if the conduit and conductors are being reused, and it doubles if they are not. Ask your contractor what wire size is in the ground now. If it was sized for 30 amp loads across 88 sites you are re trenching whether anyone likes it or not.

Girder's point about the utility contribution formula is the one people skip. I have watched a project get a five figure credit against a service upgrade simply because someone filled out the load form properly and the utility's own model showed enough new revenue to justify their share. Nobody volunteers that. You have to ask for the line extension policy in writing.

Canton, one thing I would add on sequencing. If the treatment plant has to be replaced anyway, the trenching for that work and the trenching for electrical feeders can share a mobilization if you plan them together. Doing them two years apart is how a 700k capital plan becomes 900k.

You are underwriting the upside of the 50 amp conversion but I do not see the revenue side of it anywhere in your post. What does a 50 amp site rent for versus a 30 amp site at that park today? If it is four dollars and your season is 200 nights at 65 percent, 88 sites gets you about 45k a year of new revenue for up to 850k of spend. That is a bad trade and you would be doing it for the resale story rather than the cash flow.

The wastewater is different. That is a spend you make because the alternative is being shut down. I would separate the two projects completely in my head and price the deal as if only the plant is mandatory.

Does the seller know what the engineer told you about the plant? Their answer to a retrade tells you how much information they were sitting on.

Flint's math is the part I would sit with. 45k of new revenue against 246k of pedestal work alone is a five and a half year payback before you touch the service upgrade, and that is assuming the rate premium holds and occupancy does not move. I am nowhere near a deal this size but I have started running every improvement as its own little deal with its own payback, because otherwise the capital plan is just a number attached to a vibe about bigger rigs. Canton, do you have any evidence from the reservation export that 30 amp sites are sitting empty while 50 amp sites book out? That would be the actual proof.

Run the two ends as separate deals and stop calling it one range. Low end, 4.45M basis, 372k NOI, 8.4 cap, fine. High end, 5.3M basis, 372k NOI plus whatever the amp conversion actually adds, call it 400k generously, 7.5 cap on a park you cannot fully operate during the construction year. Then subtract the revenue you lose while a treatment plant is being replaced and sites are down, which nobody has mentioned and which on a 120 site park in season is not small.

What is wrong with my version is that I have assumed the plant replacement takes sites offline. Maybe it does not, maybe it is a parallel build on adjacent ground and you cut over in a weekend. Ask the engineer that specific question before you spend the 25k, because if it is a parallel build the high end case is much less ugly and the extension is an easy yes.