An LLC is useful for two things: anonymity and legal protection.

With the internet, there aren't really do overs -- most websites have other websites that grab (legally or illegally) information . . . it is pretty impossible to make anything disappear once you put it online.

The below is not legal advice and you should hire a lawyer with past subject to experience. 

This provision, through the Affordable Homes Act, make ADUs legal BY RIGHT in any single family zoned property in the state.

What legal fees do they charge as you are now the note owner?

This creates a negative initial position.

They seem legit insofar as everything seems legal and kosher.  

Perhaps if your partner was a general contractor or handyman type there may be some merit there to reduce costs / increase profitability.If your partner enjoys deal sourcing, a better move might be for him to become an agent - so he could legally collect commissions from finding deals and managing properties for multiple people. 

Legal Implications and RisksThere are a few legal and procedural risks to be aware of:Title and Zoning Issues: Confirm there are no restrictions tied to the property.

The nuances in state regulations require an expert who understands how to expedite the process within the legal framework.