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

Or would Legal Zoom suffice?

This is rarely an issue provided you still perform.The raising money part is more complex.

This party won’t last forever, no one tells you when to get out, sometimes you realize too late. 

If you need financial help, ask under the "Finance, Tax, and Legal" forum.

I’m looking to access some of the equity in the home to buy out my ex-partner, and my goal is to either convert the house into a multifamily property or add a dwelling unit (ADU).I’d love to hear any advice from the community on the best way to approach this, particularly in terms of financing options, legal considerations, or any similar projects you've completed.

Look, I will try to simplify this: We have 3 parties money; (a) the landlord investor, (b) the lender giving a mortgage for purchase money, and (c) the tenant paying for use. 

No coaching program, called multifamily brokers in my areas, have a regular job, and have 3rd party PM.

How keep it legal of course but more importantly how to do if effectively.

This is something their screening probably would have caught, or their system would have a legal procedure to deal with it.