Under CA divorce laws, what percentage of my husband's business would I be entitled to if we were married for 5 years?

You don't give enough facts to allow a definitive answer. If the business existed before your marriage, and you were compensated for the time you put into it, it may be his separate property. If it became community property at some point the calculation of your interest would require an appraisal of the business. Hypothetically if your husband owned his business for 10 years before marriage and then it transmuted into community property for the 5 year duration of your marriage you would be entitled to 1/2 of a 1/3 interest in the business. The 1/3 is because the business was CP for only 1/3 of its existence. This is a gross over simplification. For a better answer, be prepared to spend some money on an experienced divorce attorney.

Couples in divorce court spends thousands trying to resolve this type of issue. The formula can be complicated in that it requires a valuation of the business, as well as a calculation of the community interest in that business. Then comes trying to figure out how to divide the interest for a pay off or a decision as to how to offset assets and debts. But the base information on the value of the business is the most difficult, the most crucial, and, consequently, the most expensive. And don't forget that if your husband has his own valuation and you have yours, and they are different, which they will be, then there's a battle of the experts. Your best option, to cut your losses, would be to agree on a neutral evaluator and try to either mediate or collaborate towards a resolution.

Good luck to you both.