The LLC is typically the best choice for smaller entities. The LLC structure provides a great deal of ownership flexibility in that an LLC may have any number of Members (owners) including non-US citizens and subsidiary companies. LLCs are also able to distribute several different classes of stock or ownership interest. However, their owners are typically required to pay a self-employment tax.
On the other hand, if you are not responsible for its tax, then you should declare the equipment in Part III of the Business Property Statement (Equipment belonging to others). Where equipment is declared in Part III of the Business Property Statement, the Assessor will also send a Notice to File to the person reported as the equipment's actual owner.