Before I tell you about my brother's experience as a project associate, let me shed some light on who exactly a project associate is and how is he/she selected.
The projects at IITs are funded by external bodies and are usually assigned to a Principal Investigator (PI), who has contributed majorly to the commencement of the collaborated project. This PI is usually a professor of IIT who selects students that he deems suitable to work on that project. Those who are already IITians are given the title of Project Associate. To get selected, one must check the official website for faculty and their research work. Contact the professor whose research work aligns with your interests and give a short interview before the final selection.
As a project associate, my brother was given flexibility in working hours and continuous assistance from the professors. The labs had great computational and experimental resources and made the experience easier than expected. His team had to send annual or binaural reports to the company funding his project as a part of the update. Accommodation and food would be provided by the institute itself with the permission of your professor else you will have to make arrangements outside.
It's important to note that this experience may vary from lab to lab and also your faculty advisor.