Logic tells me that we can do an addendum, however, sometimes laws defy logic.If an addendum, does anyone have a template that they'd like to share?

I think you’re hilarious.I’m sure Brad knows and can tell you that many college towns have already passed laws restricting AirBnb, just like they control the percentage of rentals in many neighborhoods and set the max unrelated adults conservatively.

On Sept. 30 a new WA state law will expand that to the entire state.  

Yet I wouldn't do it myself and would only trust it to an attorney that specializes in that area of the law.

Preferably you want to use an agent where they are paid by the tenant, but more than likely you would have to pay one if you choose to use one.If you do not use one, just be very mindful of fair housing laws which are a huge issue in your market.

If you do, it should be strictly a simple lease. 

They are also subject to rules governing service termina­tions to multiple dwellings, customer security deposits, payment agencies, back-billing and the refund of overpayments.Municipally owned water suppliers (those of cities, towns, villages, etc.) are not governed by the Public Service Law.

I put myself on a strict budget and if I didn't have the money, I had to find ways to have fun that didn't cost anything (having friends over for game night, going to the park, renting a video, etc).

I will be using a private money lender - my father in-law.

Regarding your question about the deposit, typically, it is best to address the security deposit issue after the current lease expires, laws do not require tenants to sign an addendum for anything during the course of the current lease.