For everyone's sake, sit down and have a nice long chat about what to expect and what you want. Sitting down face to face will make sure you guys get along and can form a nice partnership. Assuming you have found the perfect photographer who shares your vision and style and price range, come up with a detailed outline of what you are getting and what it will cost. A professional photographer will require at least a deposit at booking, if not the full amount.
Most will charge by the item, or a day rate (day rate will be the cheapest normally) - you need to have a clear vision of what you want out of your photos, even an example to ensure your photographer is on the same page as you. If you require a model for your photos, the price will jump drastically - chances are you will have to pay for the model (unless you have someone who will sign a contract and do it for free)!
I did product photography for local boutiques for a couple years, advice from the photographers perspective - KNOW WHAT YOU WANT, and clearly communicate that at the beginning. Nothing is more annoying than saying 'I want a white background' - shooting on a white background, and afterwards saying "can we change the white to pink"? Doing this can destroy a potential partnership very quickly. And please, do not shop by price entirely - obviously its a huge influence, but going with a photographer that you don't like their style but you do like their price, and demanding they change their style for you is horribly disrespectful.
