Conversion of buildings' use has an ancient history
Midtown Is Reeling. Should Its Offices Become Apartments?
https://www.nytimes.com/2020/12/11/nyregion/nyc-commercial-real-estate.html
Conversion of buildings' use has an ancient history, perhaps as long as there have been buildings. So too multiple uses within buildings, as well as alternatives and renovations and updates, sometimes before a building is finished and continuing thereafter.
Building codes are quite responsive to these transformations, along with construction practices, financing, professional designing, changes in taste, ups and downs of businesses, leases, disasters, masters of renewals and innovative interventions and investments.
Zoning regulation is rife with exceptions, modifications, interpretations, novelties, accommodation of hardships, susceptibility to aggressive dealmaking, lobbying, replacement of commissioners, special districts for a slew of interests, hardly unchangeable at all.
A handsomely paid and politically connected industry exists in NYC to massage all its codes to oblige interest groups, wealthy, poor, middling, foreign, ethnic, racial, gender, designers, investors (always those, goodly number anonymous).
Great swatches of NYC and all the world's urban agglomerations are composed of converted buildings, industrial to commercial to residential to museum to artist studios to homeless stashes, nothing out of consideration although accompanied by the customary bleat of those who pretend to oppose change but who jump at the chance to enjoy a pretty penny windfall.
Mask against blowing gypboard dust, watch out for airborne masonry, aged greenbacks vs. newby bitcoins.