My tenant is a SPC need help on evicting them

I had let the tenants move in to my rental apartment on September 15th of 2016 and till this day they don't have leasse agreement contract between me and them. They lived in a Hotel for almost a year and depleted their savings and I let them move in for free till they get on their feet and now its been 14 months. I had asked them to pay six hundred a month and they said there not not gonna pay rent and they will not move out, I did ask them to pay for their gas (38$/mo.) a few months back and that's all their paying. Should I try to have them sign a rental agreement contract ? Someone said not to cause I can evict them quicker. Beings they are SPC's I don't know what tactics they gonna retaliate against me. Thank you.