How to ask my advisor from another department for research assistantship? I'm a first-year Machine Learning PhD student supported by a TAship offered by my host (non-ML) department that does not have much funding. I have heard that RA is uncommon in my host department. A professor from the CS department (renowned for its ample funding) has recently committed to be my thesis advisor, and I was wondering if he would be able to give me research assistantship in the future if my research becomes successful. To be honest, I am not 100% sure whether a professor can give a RAship to a student from other department. If it is possible, could you describe how to ask, so that I can follow the advice once my research becomes successful? Is there any general understanding about from what year it is reasonable to have RA in CS and what the reasonable RA duties in CS are? Is RA something to be offered rather than to ask for?
Just ask.  Generalities from the Internet are not going to be so helpful here.


  Would you be willing to consider me for a research assistantship at some point? 
  
  What would you expect me to accomplish to get to that point? 
  
  If I had an assistantship, what would you expect me to work on?  Would it be part of my dissertation research?  If not, how should I plan to balance the two?
  
  Given that I'm enrolled in another department, are there any bureaucratic obstacles to this, and is there anything I can do to help with them?