Assuming you are talking about the US federal Freedom of Information Act, there is a category of "commercial use requests" mentioned in the statute at 5 USC 552 (a) (4) (A) (ii) (I):
fees shall be limited to reasonable standard charges for document search, duplication, and review, when records are requested for commercial use
For non-commercial use, you only have to pay for search and duplication (and requests by journalists and scientists only have to pay for duplication). So if this is for commercial use, you can still have the request fulfilled, but it will cost you more.
"Commercial use" doesn't seem to be defined in the statute. However, each agency implements this process with its own regulations, and in some cases they give more details as to what is considered "commercial use". As an example, the Department of the Treasury has its regulations at 31 CFR 1.5, and paragraph (b) (2) (i) says:
A commercial use request refers to a request from or on behalf of one who seeks information for a use or purpose that furthers the commercial, trade, or profit interests of the requester or the person on whose behalf the request is made, which can include furthering those interests through litigation. The bureaus may determine from the use specified in the request that the requester is a commercial user.
So if this request furthers your "commercial, trade, or profit interests" or those of your clients, then it's a commercial use request, and you'll have to pay accordingly.
