Criteria to evaluate consulting opportunity You're an academic researcher who has done some work in a particular topic.  You receive an email from a stranger, working at a small company, interested in your work and wanting to discuss possible consulting.  Sounds interesting, but you have research to perform, grant proposals to write, classes to teach...

What criteria should you use to evaluate whether or not this is worthwhile?  What are things you look for in possible consulting work? And what are turn-offs and things you want to avoid?
Balance is always tricky but basically the guidelines that I follow are:


If the consulting will help me learning something new, +1 
If the consulting will pay me a lot of money, +1 
If the consulting will improve my reputation, +1 
If the consulting will allow me access to something I want (new data), +1


On the other hand, 


If it takes a lot time, -1
If it offers little or no pay, -1
If it could damage my reputation, -5
If it would be a bit boring, -1


In the end, I just do the math.