River, whose reptile rescue occupies two large studios, is one of the more unusual tenants.
He says his “fascination with reptiles and exotic things” began as a child in the Netherlands.
He moved to the UK at the age of 11 and, after a spell as the singer in a boyband, found himself homeless.
After getting back on his feet, he began taking in animals that friends and acquaintances could no longer look after.
“It quickly grew into a big passion and I realised there was a need for someone to take in reptiles in Scotland,” he says.
His rescue centre has grown significantly in the years since and he says St Margaret’s House is an “incredible” place to be.
“The community here is just phenomenal, everyone supports each other,” he says.
The news of the building’s sale has been difficult for all the tenants, some of whom have been there for 18 years, he says.
“Everyone is trying to help each other through, but it’s really put stress on us all,” River says.
The Scot-ART tenants were informed on 28 September that they had to vacate the building by 24 January.
Building owners Caledonian Trust told the BBC they had “fully communicated” that St Margaret’s House had been on the market for some time.
“We’re in discussions with a preferred party, but the process isn’t finished and it would be inappropriate to provide any more detail,” a statement said.
The owners said Scot-Art had leased the building for many years on “generous terms” and they had been proud to support independent artists and freelancers.
However, they said that the building no longer met the standards needed for its long-term future.
Scot-ART said they were “incredibly proud ” of what they had achieved by supporting diverse grassroots and creative arts organisations over the past 20 years.
It said was working hard behind the scenes to build a more resilient and long-term future.