A single person LLC document is one where it probably makes less of a difference to have it drafted by a lawyer than many other documents because it has very few tax implications and governance is elementary. The main issues would be choosing a proper LLC name and correctly choosing whether it should be member managed or manager managed (almost always, manager managed is preferred).
But, the main reason to consult a lawyer is to determine if a single person LLC as opposed, for example, to an S corporation, is really the most appropriate entity form for your business.
Among the concerns would be how this form would interact with California's community property laws, determining whether the LLC is disregarded for state franchise taxes as well as federal income taxes, determining what impact the LLC makes on Medicaid planning and estate planning, determining whether the ability to reduce FICA taxation in an S-corporation makes it worth choosing that form rather than an LLC, determining whether there are liability insurance requirements that are triggered, and determining how this form impacts health insurance structures v. other alternatives.
An attorney could also advise you on the "care and feeding" of the LLC so that you are clear on how to observe the proper formalities. For example, many people forget to, or don't know how to, title property in the LLC name, don't know when to obtain a separate EIN for the LLC, don't know how to sign documents in the name of the LLC, don't know how to draft an LLC authorization, don't know that the LLC must be an insured on insurance policies, etc.
Also, an attorney normally wouldn't charge very much for a very simple entity like a single member LLC Operating Agreement.
My rule of thumb is that getting a lawyer to fix a problem after the fact caused by DIY work by a client is about ten times as great as the cost of hiring a lawyer to do it correctly in the first place.
For example, a single person LLC might cost $500-$750 to draft in the first place including a consultation about whether it was really appropriate and a care and feeding discussion. Fixing a problem caused by inappropriately using a single person LLC might typically cost $5000-$7500.