It looks like you’re asking two questions. The going pay rate for an employee is going to be different than the going pay rate for an independent contractor, and if you’re going to be renting space to them, then what they make will be irrelevant because you have guaranteed rental income of whatever you charge.
What you might want to do is check with other studios that rent space in your area and find out what they rent for based on the studio size, equipment, amenities, etc.
Also, are you on Facebook?
This group is for the pacific northwest and has a lot of instructors in it from your target area. You might join and post there, both for advertising your jobs and your questions about pay.
I’m in Portland OR, and the going rate in PDX for an employee instructor is $18 – $40 an hour. Contractors get paid more than that to account for the higher taxes. Renters pay fixed rent and then collect whatever they collect. I’ve been an independent contractor yoga instructor where I paid rent of $30 – $50 per hour and collected all the money that I made. I’ve also been an independent contractor yoga instructor where I received a commission of $4 – 6 per person who attended.
But again, PDX could be different than Federal Way. You could make a case that since it’s near Seattle, rates would be higher. Or you could argue that it’s not all that different since it’s distant enough from SEA that it wouldn’t have the higher cost / revenue you’d get in downtown SEA.