Managing seats

Hi there,
I am about to purchase either Pro or Studio licence but wondering how much does it cost to add extra seat as well. I have an assistant who would use sketchup for my projects. I see that with one licences we can’t both be workingn at the same time so wondering what is the most cost effective way to have the extra seat on the same licence?

The extra seat would cost the same.
Maybe your local reseller gives a discount for extra seats but you would have to ask them…

OK, thank you.