Unfortunately, this is one of those questions where the answer is "it depends."
Most attorney reviews of commercial leases are done on an hourly basis, because the lawyer has to do several things. It starts with understanding your business and the attendant risks and goals associated with the business. From there, the lawyer needs to review the lease in detail to determine whether any of the lease terms conflict with your goals and/or expose you to unreasonable risks. The lawyer would then discuss the issues raised in the document review, and would likely draft a form of Lease Addendum based on that discussion. Finally, it is likely that you would require the lawyer's assistance in negotiating the final terms of the lease, as commercial leases are very heavily negotiated documents when both sides are represented by competent counsel.
That said, if your lawyer is also a real estate broker, then you might be able to bring the lawyer in as your agent (assuming you don't already have an agent), and the lawyer could get paid through leasing commissions. I have done this for clients in the past, and it can minimize or even eliminate the amount you come out of pocket, so long as you actually end up leasing the space and the lawyer gets paid from leasing commissions.
Please note that, while I am a lawyer, I am not your lawyer. This information is for general educational and informational purposes only, and is not legal advice. You should review your particular situation with a qualified lawyer of your choosing.
Most document review is typically billed at the attorney's hourly rate. Depending on what you want (eg. a simple review v. negotiation or drafting changes) the cost could vary dramatically. A straightforward review of a standard commercial lease usually takes a couple of hours and you may be able to find an attorney in your area to do it for a flat fee.
The information in this posting is for general information purposes only. No part of this posting should be taken as legal advice for any individual case or situation. This information is not intended to create, and receipt or viewing of this information does not constitute, an attorney-client relationship.
While our office regularly does this for Los Angeles tenants, you may wish to consult San Diego counsel in case there are any local regulations that other attorneys would not be aware of. Hillary Johns is a San Diego business attorney who regularly posts on Avvo.
The above is general legal and business analysis. It is not "legal advise" but analysis, and different lawyers may analyse this matter differently, especially if there are additional facts not reflected in the question. I am not your attorney until retained by a written retainer agreement signed by both of us. I am only licensed in California. See also avvo.com terms and conditions item 9, incorporated as if it was reprinted here.