A Phase I environmental site assessment is a records-and-eyes review done to a published standard called ASTM E1527. The consultant pulls historical aerial photos, fire insurance maps, city directories and regulatory databases, walks the building, and interviews people who know its history. No sampling of soil or groundwater happens in a Phase I. On a single 12,000 sf building expect roughly $2,000 to $4,000 and two to three weeks, faster if you pay a rush fee.
If the consultant finds what the standard calls a recognized environmental condition, they'll recommend a Phase II, which is where drilling and lab work start. That's a different order of cost, commonly $10,000 to $50,000 and up depending on how many borings and what they're testing for. A 15-year body shop with a floor drain is exactly the fact pattern that produces a Phase II recommendation, because solvents and paint waste going into a drain is a known pathway.
On the protection point, a Phase I performed to the standard is one of the requirements for certain purchaser defenses under federal cleanup law, and there are continuing obligations after closing too. Whether you actually qualify depends on the specific facts, so that's a conversation with an environmental attorney rather than a broker. State cleanup and disclosure programs sit on top of the federal rules and differ by state.
Two practical things people miss. The report generally needs to be in your name or come with a reliance letter, so don't rely on the seller's old copy without one, and reports go stale after about six months. Your lender will probably also want a property condition assessment, a separate engineering report on roof, paving and mechanicals, usually $2,500 to $5,000.
