Are you sure that you need to be bonded in order to clean where you will be working? I have never known of a cleaner that needed to be bonded. However, I suppose that it would depend on the location and whether or not any of your customers are requiring you to be bonded.
How much it might cost would depend on the type of bond that you need and where you are located.
There is also the following search that you might try.
Cost of Bonding Insurance - Google Search