How to know whether a visiting professor will charge the university to present a lecture to academic staff? In the faculty that I am currently working on we have contacted a Professor who would be giving a workshop in my city. Because of that we have invited him for a meeting for discussing collaboration issues for making research in his area of expertise. Also he would be willing to give a lecture to the lecturers of our faculty about the current trends in his research area.

The question that I have is how to know if this lecturer will charge us for the lecture? It is in the field of Computer Science. If this is the case we need to make the necessary administrative paperwork to cover this expenses (my place of work is very bureaucratic by the way). This lecturer has not mentioned anything about charges so how we ask him nicely if he would charge anything for this meeting and lecture? also what would be the necessary arrangements that we should do in this case?
The usual way is to state explicitly in your invitation which costs you are going to cover. For example:


  Dear Professor X
  
  I would hereby like to formally invite you to give a seminar talk at our university on a topic of your choice. We will of course provide you with a hotel for your stay as well as cover your airfare and all other reasonable travel expenses.
  
  Sincerely,  Y


This way, it is clear to everyone what exactly you intend to pay for. If Professor X wants anything else, he will have to ask for it explicitly, and you can then choose whether you think that you want to pay for that as well or not, but at least you put out there what you expect to pay for.