Do you need to be a 'green card' holder or a US citizen to start a small business in San Diego, California? My permanent residency is still in process and I am still on H1-B Visa. I'm planning on starting a sole proprietorship or LLC structural consulting engineering business in California.
There are no citizenship or residence requirements for ownership of a C Corporation or an LLC in CA. LIkewise, if you form a sole proprietorship and file "DBA" fictitious business name, you don't need to be a U.S. citizen.
Please see the guide linked below. You may also want to see a business lawyer about choosing the best entity for your business, and for the other things you need and want, like licenses, insurance, contracts for your clients, a trademark, a domain name, etc,. etc., and you may also need to hire a CPA to do the business's taxes.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.