it could be done, although to be freelance you really need some experience in the job first, most researchers have been production assistants before becoming researchers, although that's not set in stone. look for training courses - 'skillset' is a very good traing organisation, also the bbc do excellent training courses. 'broadcast' magazine is the tv industry paper and comes out every thursday it has a training section in it. for experience in low/no paid work you could join www.shootingpeople.com and put your details up on their site, you also get daily bulletin boards where people advertise for help.
good luck