Does a PhD student get paid without a TA/RA job? Can a PhD student be paid simply for doing research?
If yes, is it applicable right from the beginning?
I am talking about UK and the US specifically.
Can a PhD student be paid simply for doing research?

Yes, in the US, this is often called &quot;being on fellowship,&quot; when the research is your own, and an &quot;RAship&quot; if you are paid to work on another project at a professor's discretion. Fellowships are often prominent national opportunities, but can be funded locally by the university, college, or department.

If yes, is it applicable right from the beginning?

This is entirely dependent on what the program offers you. It may be, it might not be. Some departments offer first-year fellowships so that you can get settled in your program.