Personally I imagine that there are definitely charm-casting professionals who do it for a career, like Lynn's Alasdair w/illusions!

And when it comes to space altering of buildings in particular, I'd imagine that falls under the purview of magical architects? Seems like the sort of thing you'd learn apprenticing as one and yeah, want to be appropriately qualified to do, and more permanent charms in buildings probably can last longer but probably also need structural check-ups once a decade or whatever to keep them in check so they don't fall in. My headcanon, anyway xD