I stated I had a lease agreement and a separate option agreement (the paperwork was done right).

Essentially now you're going to have to rely on your accountant to examine your process and agree with you.

What sort of zoning paperwork would be required on my part to make that a "2 unit" property down the road, assuming it's not just an airbnb gig?

I just want to have all my paperwork reviewed to make sure I have everything in order and is on the up and up.

Congrats @Austin Fruechting, I've been reading through your blog as well and I agree knowing your "why" is absolutely essential.

The way I calculate ARV is by essentially looking at sold properties within last six months in close proximity, and similar age.

Let me be clear, I am not asking about bookkeeping such as maintaining cashflow, expenses, etc.As a buy & hold investor with a couple rental properties, what forms/paperwork/etc do others hold onto in the form of HARD/PHYSICAL COPIES vs.

Essentially, the law says that when you rent a property, you make an implied promise to the tenant that the property is in a habitable condition.

With Any situation you could "what if" it forever and no matter how perfect your paperwork is, someone can still go sideways, someone can still default, someone can still sue you. 

I am trying to build a portfolio of real estate and would like to be able to refinance, pull equity out and purchase another property and essentially follow the typical Brrrr strategy going forward (rent out the next one right after reno).