Haha I was sort of just joking, as a worker in the creative arts. But you're correct, with the flexibility of English, 'creative' might be modifying 'professional' in the sense: creative when coming up with ways to avoid paying taxes.
Either way, I looked up the prices in PlusColonia, and you can get a 35sm studio for $70,000. So it's not impossible, just unlikely that a bunch of struggling libertarian painters and musicians will move there to add flavor.
This is a strictly plebe concern, but what happens if the government of Uruguay sees fit to change tax policy in the future? They would just take the loss or do short term rental of their property; what's a couple million if you have a billion.
If it were to succeed (big 'if' when it comes to utopian city projects), we'd see a lot of fancy boats coming across the river to BA in the evening. Not a lot of nightlife in Colonia. Or they'd buy a pied a terre, like Peter Thiel.