There are a lot of misconceptions about the protections afforded by the LLC, so speak with an attorney.

In this case, he gave us ample notice to (most likely) fill that slot, however, I'd like to protect us in the future.

Too many in your shoes over complicate real estate and spend unnecessary time and expense on tax planning & asset protection and in doing so, take away from the real estate.

The beneficiaries are all hidden from 'adversaries' who may want to sue you, but you must pierce that veil of protection when it comes to lending. 

Research the appropriate laws for your property and follow best practices to avoid any discrimination accusations: use the same criteria for everyone who applies, know what the protected classes are, which questions are legal to ask and which aren't, and only deny applicants for legal reasons etc.

You are marketing a deal that isnt really protected in anyway and could be stolen right from under you.

Hi,If I buy a apartment doing a seller carry back, how do I explain to the seller how they are protected if they carry a 2nd position note subordinate to the bank?

He has asked;"Provide protection around water heater or furnace to prevent children from making contact with theseappliances."

Any advice or pitfalls that I should prepare for or protect myself from?

You’re on the right track—setting up separate LLCs for wholesaling and building can simplify things and offer liability protection, plus putting properties in their own LLCs keeps assets safer as you grow.