This is one of the first things that professional commercial photographers will ask you about. This is mainly because of the fact that they can actually learn so much about a potential project with a simple walkthrough of the budget that the client has allotted for it. If you have next to zero idea about how commercial photographers work and about how you should price your needs, then try to go for a sensible ballpark figure. Let your photographer know that you are willing to adjust it every now and then if the argument is sensible and if it will be explained to you thoroughly at the end of the day.
There is no one size fits all when it comes to commercial photography and the budget that it may eat up. It is all a balance between where you are as a company right now, what is the common perception of people about your product and services, how much effort and prep the commercial photographers will need to bring in to the deal, and so on and so forth. Try to make the best guess that you can put in about the amount of the service that you will be paying for at the end of the day. Of course, you come up with a budget that you can easily afford and work your way slowly through from there.
The scope of the coverage
You have to understand that your photographer needs to know how extensive the coverage and the exposure will be for the photos that are being produced. Are they meant to be used internally for the company and its employees or are the photos meant to be branding and marketing material? The differences between the two can be quite stark and glaring. It is pretty easy to understand why a commercial photographer will charge you something so much higher if your photos are meant for a national ad campaign as opposed to when you are just planning to post the photos on the ads section of your local newspaper.
You have to be there every step of the way and you have to see to it that your visions are actually being carried out accordingly or this may never work. You will end up going back and forth and fighting your photographer while you are at it. Suffice it to say, it is not an ideal way of working through the photo shoot if there ever will be one. It will be more practical for you to be there during the day of the shoot so that you can share your two cents on certain things as well as on certain ideas.
A legitimate commercial photographer will always make sure that he presents you with a contract or some kind of document that will make your deal legit. Go over the contract and make sure that you understand everything before finally designing to sign it. Be as detailed as you can when you are reviewing your contract because it will gauge how much you will be getting from the deal and whether or not it will be worth it all in the end.