Recently, Union City has amended their rent control laws to include 3-family non-owner occupied houses.

--Amend the lease.

I would, of course, negotiate this with them and get it drafted as an amendment and signed.

It does not address amendments to the code.Every sleeping room requires a hardwired smoke detector with battery backup.  

The operating agreement could be amended for a new partner.

Do you create an amendment to the original lease to add the extra adult?

If said person were to join an LLC by amending operating agreement to establish ownership or a decent amount of ownership of an  LLC that has ownership of 393 units bought 20 years ago would the experience of that ownership be transferred to the member that has just joined?

You can still share other buyers offers with everyone who submit offers if you'd like to see if anyone will amend their existing offer later if you think you have a strong enough property in higher demand.

Finally digging through the dol.gov, found a helpful link: http://www.dol.wa.gov/business/realestate/assistants.htmlI see that you don't need a license if you are:Property management assistantsUnlicensed assistants who provide property management brokerage services for the owner, designated broker, or managing broker may perform the following tasks and duties:Unlicensed assistants may… Deliver lease applications, leases, or any amendments.Receive lease applications, leases, amendments, security deposits, rental payments, or any related payment for delivery to, and made payable to, the owner or real estate firm.Show rental units.Execute leases or rental agreements, rental payments, or any related payment for delivery to, and made payable to, the owner or real estate firm.Act as a scrivener, completing blanks on preprinted and preapproved rental agreements with the exact language provided by the property owner, designated broker, or managing broker.

thank you all @Steven Hamilton II and @James Syed for the replies...looks like I need to go back and amend last years return and get an extension for this year.