I put money down on a trailer and weeks of waiting/calling i found people were there and no work had been done. Now he says i cant have my money back

I put money down on a trailer in November of 2016 and was told we could move in by the 1st of December 2016. After weeks of waiting and calling to get updates an make sure we could still move in I found out. The previous tenants were still living there an no move out date was givin to them and no work was done to the trailer. So the move in date was set back to the 5th I didn't like it but decided to give him another chance. I waited an aditional week called him back an nothing had changed, so I asked for my money back he was hesitant at first but said he'd send a check i questioned this cause I paid cash he said thats how it works. It's now been 2 1/2 weeks since that call and still no check has come I call him an get told he's not giving my money back because he leagly doesn't have to an because I prevented him from renting to someone else. I called the police to see if they could help but they said they couldn't What can I do to get my money back?