Best practices for quarantining orchids in small space

[Polypodiaceae]

I have a 450 square foot studio, so have been pretty careful about where I orchids and know I'm rolling the dice. However, I'm seeing some perfectly nice phals on Craigslist etc that are good prices. Seattle's pretty temperate this time of year, so considering quarantining them outside, in a shady spot, for several days and good inspections. Seems like a decent balance of "protect what you have" and "carpe diem cheap plants" given my space limitations. Interested in what others have done to quarantine in small spaces and/or if this is a terrible idea.