The PC 182 is a conspiracy. The potential sentence for a conspiracy is the same as the crime one conspired to commit. As you mention no other crime except a residential burglary, the sentence could be 2, 4 or 6 years in prison. The 459 is a mandatory 2,4 or 6 years in prison except in unusual circumstances. Depending on the facts, I believe that the time would run concurrent as to each offense (6 years). If run consecutive, 7 years 4 months.
Good luck to your nephew. Hope some one can find him a good attorney. Good would be one with negotiation skills.
In any criminal case, how much time a person is sentenced to depends on many factors. First, the facts of the case. Next will be the person's prior record (or lack thereof); whether or not any restitution has been paid in full up front or not, etc.
I read your question to be that your nephew was caught in a house. If it was an inhabited residence, then he's looking at first degree burglary. Unfortunately, that's a strike under California's three strikes law and he is presumptively ineligible for probation. The minimum sentence is 2 years in state prison. A judge can find unusual circumstances in order to grant probation and not sentence him to state prison.
The 182 is conspiracy. The sentence for conspiracy is the same as the target crime. I assume that the conspiracy here is conspiracy to commit burglary. If so, the two crimes merge for the purpose of sentencing and no additional time would be imposed.
The fact that he's accused of conspiring with another will weigh against him as an aggravating factor, potentially making the case look more sophisticated and planned (versus spontaneous).
Bottom line: Your nephew needs a very good criminal defense attorney who routinely practices in the court where his case will be heard. This is not a situation for your neighbor who happens to be a lawyer to try and resolve this case... unless they focus exclusively on criminal defense.
One thing to remember is that the charges the police wrote on the ticket may not necessarily be what the DA charges him with. The District Attorney has discretion when filing charges, and some DAs will meet with a private attorney before they file the charges to hear the attorney's opinion. Public defenders, however can't do anything until the arraignment. So it would serve your nephew's interest if you contacted an attorney soon.