Under CA divorce laws, what percentage of my husband's business would I be entitled to

In your question you did not state whether or not you will be seeking a divroce soon. I assume that you will be. You have several options but depending on the circusmatnces there may not be much community property in the partnership if it was just started unless there was a large infusion of capital. One option is to insist that you be added as one of the partners in the partnership agreement with full rights to review the books. You should conuslt with an attorney to draft this since you'll want provisions for withdrawing from the partnership account in the event of a divroce. Also you can ask for him to sign a post nuptial agreement that receive half of his partership interest as community property and try to determine what that interest is now. In the absence of either you would still be entitled to a community interest in the partnership but you would probably need to retain the services of a forensic accountant. This amount may be minimal.

If your husband starts a business during the marriage and you ultimately get a divorce, then you will (with some limited exceptions) receive one half of the community interest (value) in that business.