Are professors typically financially compensated for advising masters theses? I have a professor that has given me some early advice on developing my thesis topic, but I have not yet formally selected a thesis advisor. I was thinking about choosing to work with a different professor whose research seems slightly more aligned with the project, but I'm curious if my professor (the one I already spoke with) will expect me to work with him, and if this would have entailed some sort of financial compensation for him. Not that this would heavily influence my decision, but it's something I'd like to be aware of.
Yes.  It is called a salary.  And advising is one of the duties listed when the job is offered.