Nobody can give you a meaningful answer without knowing all the facts. Commercial burglary can mean anything from walking into a store with the intent to steal a pack of gum, to breaking into a business at night and stealing thousands of dollars worth of merchandise.
Second degree burglary is a "wobbler" that can be charged as a felony, with a potential prison sentence ranging from sixteen months to three years, or a misdemeanor with up to a year in jail.
His lawyer is in a much better position to answer this question. If he can't afford to hire his own, the judge will appoint the public defender.
His lawyer presumably has the discovery (police reports, etc.), has spoken to the District Attorney and the Judge and knows the case and the likelihood of what kind of time in jail/prison, if any, he is looking at.
Your boyfriend's exposure could include anything from 3 years in prison to probation depending on the facts of his case.
The fact that he doesn't have a prior record will certainly work in his favor. In order to truly limit his exposure and get the best deal possible for his case, he should try to hire a criminal defense lawyer familiar with the court in which his case is filed. I can't stress enough how important it is.
I wish I could say more about how much jail your boyfriend may be looking at but it just isn't possible based on what you have provided in your questions.
Long Beach is not a compassionate jurisdiction. The DA could reduce it to a misdemeanor immediately or he could "earn" a misdemeanor by successfully completing probation and filing for a reduction and expungement. With no prior record, probation, time served and restitution could be an outcome.