Want to cancel RV sale as wife lost job - how can we?

I hope I am wrong, but I wonder if what you signed, was equvelant,to putting earnst money down on a house. You signed it, the dealer signed. So the deal would be agreed to. You may have had, just as you would with a house, chances to get out of it. Like if failed inspection etc. But By cancelling the check, I hope your are not now in direct breach of contract