Hi,
I am looking to do a masters in finance.
My background:
MS environmental engineering
B.Tech civil engineering
(Half an year of industrial work experience and 20 months of working as a research assistant (4 months as voluntary work))

I am not sure whether I can include my research experience as work experience in my application. Can someone help me on this ?

The paid time is work, but normally they will look only at work after your graduation. The good news is that 90% of MFin programmes don't require work experience.