Yes an attorney can help you file an application and seek the variance. An attorney will give you the best chance if you have a chance.
This is not a comprehensive answer and it is impossible to provide a meaningful response without a consultation. Call us for more information. 619.797.5456 www.mataelelaw.com
You should talk to a local Fremont CA attorney - this is a national listserv. An attorney can help you work through the details of your local code as it relates to your specific project. Unless you think you will raise some red-flag issues that will be a problem later you might also start with going to the local planning/community development department for the City and see what they will allow under the code, and if they identify problems then seek the assistance of an attorney.
I strongly suspect the only hope for success you have is by going through a local experienced Fremont Real Estate attorney who has dealt with the City zoning codes and Planning Dept. As a life long resident in Fremont, and an attorney practicing in Fremont for 35 years, your facts sound somewhat unusual in that you have a permitted unit in front of a main house with a separate entrance. Was the front unit ever used as a resident? If so, for how long? If not, what other use was it put to? Are you quite certain there are building permits allowing said unit? Are you aware of any sit-back requirements in regard to neighboring property or the front property line? What intended use do you plan for this front unit? Is this building presently used? If so, what is it used for and for how long? If not, how long has it not been used? If so, what was the previous use of the property, and what were the date of said usage? These are questions that must be answered before a local attorney can intelligently address your specific issues.
This participating Attorney does not warrant any information provided, nor are we creating an Attorney-Client relationship by providing said information to you on this site. Nothing contained herein is intended to constitute, offer, induce, promise, or contract of any kind. The content provided is presented as a courtesy to be used only for informational purposes and is not represented to be error free. The Law Offices of John N. Kitta makes no representations or warranties of any kind with respect to its answer to inquiries, and such representations and warranties are being expressly disclaimed. Given limited facts, we are attempting to share relevant information concerning this area of the law as a public service.
Before retaining a land use attorney, I would recommend that you personally go to the building department and ask for information regarding your question. I would suspect that under the facts you raised, the building department will require a variance application. The building department may also provide you with specific information regarding allowable uses.
Once you have received feedback from the building department, I would then contact a land use attorney who would double check the information you were provided and assist you with the application process.
Best of luck in your music instruction business!