Definitely get your money first. I used to do a double glazing factory, they always paid for two visits in arrears. I turned up to do them on the second visit (so they owed me for the previous one). The finance director came out as I was doing them, gave me a cheery "Hello there!" and walked away. I put my invoice in to the office as usual and nobody said a dicky bird to me. A couple of days later I read in the local paper that they had gone bust. I never got paid, even though I filled in the claim form sent to me by the administrators. Apparently I wasn't high enough priority on their payment list!