Where to become a sole proprietor...

Hello, 

 

Considering starting a telehealth therapy business and living in California. All work would be done virtually in Oregon. Does anyone know if I also need to become a sole proprietor in Oregon if that is where my customers are based? I know regardless I need to become one in CA since I know they are particular but have been confused about whether I need to have the same stuff in OR. All of this boils down to taxes....