Top Law Schools

Would it make me more competitive? Want to work in civil litigation/probate/family law in California. PI license doesnt seem to difficult to get, and id think that something like that would be beneficial to a firm. Thoughts?

I'm not sure exactly how it would help. You couldn't be an attorney and investigator on the same case, because an attorney can't testify - if an attorney is going to be a witness in a case (like an investigator seems likely to be), they have to be taken off the case. (The attorney can't be the person who keeps the evidence in the chain of custody, either.) So it seems to me you'd do them the most good as either an attorney or an investigator, but not both.

But I don't have any direct evidence about this, so am happy to be proven wrong.

I imagine it would rarely if ever be something you used, but how low cost/time are we talking here? It might be something like a notary, real estate license, CPA, bar admissions in obscure jurisdictions, etc, where on a day to day or even month to month you never use it but on that one occasion when you do, it proves very valuable.

That being said, I'd lean toward not bothering. I'd be concerned about what A Nony brought up which is basically blurring the lines between your role as an attorney and your role as a PI in this case. You don't want them to devalue your contributions as an attorney since that is almost surely the higher paid of the two roles.