Pls clarify how the process go. Like if u are in a lab, how your tuition and living expenses covered typically,
and typical amounts/rates currently they pay in US.( should I bargain or just accept what he's saying?)
Basically you can talk to your department office and clarify how the process, start/end and pay rates for your position (if your professor already notified this to the office). If the position is a TA, then things are same for all the TA's (same pay rate, no bargain at all

). If your position is a GA or RA, then this depends on the availability of the funds. If your professors already decided how much he is going to pay (normally this will be same for people in the same lab in the same position), based on may be a written grant?? You need to talk to him and see.
From my personal experience, I used to work in a different department GRA position before joining the lab. The previous place used to pay me around $1225 and I found the lab RA's are getting only $1125. (I found this info from the office administrative coordinator, they are the one who do the paper work). I talked to my supervisor and mentioned I used to get $1225 and he agreed to pay the extra amount from his personal grants
If the funds are from the department, then the pay rate is usually the same for all the RA's in the department. Otherwise there is a possibility that based on the bargain power, some may have different pay rates...........May be you can talk to other RA's in the lab and see how much they get paid before talking to your professor
