If something can only be one of two things, this is a Boolean (“yes/no” in Bubble terminology). And you define the field by one thing being in opposition to the other.
So a Client is either:
- Paying no / Paying yes … or…
- Probono no / Probono yes
… depending upon which you think is more common. So you set up a Client like so:
- Either a Client has a field called “Paying” (a yes/no) … or…
- A Client has a field called “Probono” (a yes/no)
More about Booleans: Video: Working with Booleans (yes/no values) in Bubble - Are YOU Cool with Boole?