How can a person buy a 4-unit multifamily property, live in one of the units and have the property owned by their LLC in a way that would prevent the

This is entirely proper.  The LLC rents to the member of the LLC.  Maintaining the liability protection afforded by the LLC is a factor of lots of other issues but renting an apartment in a building owned by the LLC -- by itself -- does not jeopardize the liability protection of the LLC.  You should have good leases with the tenants and good insurance to protect you.  You should also observe some basic do's and don'ts common to LLCs to ensure that you'll get the protection you're seeking from the LLC.