Rough ranges first, then the trap in your last question.
A Phase I environmental site assessment is a records search and site walk by a consultant looking for signs of contamination history. On a single building in most metros that's about $2,500 to $4,000. A property condition assessment, or PCA, is an engineer's report on roof, HVAC, elevator, paving and accessibility, usually $3,500 to $6,000 at your size. An ALTA survey, which maps boundaries and easements to a national standard, runs roughly $3,000 to $7,000 and varies a lot by state and surveyor workload. A lender appraisal on a $3.6m medical building often lands $5,000 to $8,000, because the appraiser has to build medical rent comps rather than pull them off a sheet. A zoning report is a few hundred. Add legal for lease and title review.
So plan on $15,000 to $25,000, and treat most of it as spent money the moment it's ordered.
On reusing the seller's Phase I, sometimes yes for your own information, usually no for the lender. Lenders want a report addressed to them from a vendor they approve, and consultants generally treat a Phase I as stale after a set period. You can ask the seller for their old reports anyway, because they tell you what was found last time for free.
One thing worth asking about early in a medical building specifically: prior x-ray processing chemicals, dental amalgam separators, and sterilizer or lab drains sometimes push a consultant to recommend further sampling. A Phase II with soil or drain work starts around $10,000 and adds weeks. Ask the seller what uses have occupied each suite since the building went up.