Usually when a gemini is parceled separately, but have a common wall, there is some type of separation line so each owner knows where their property (and responsibility) begins and ends. 

For plumbing they generally (it's different in different cities) will pass the rough in inspection first, then you have to do the other stuff (like install the bathtub and fill it with water) and pass that stuff before you do the wall tiles etc.  

I assume numbers are needed for a full answer but I am new to this and now wanting to learn and not waste anymore money.

You can join WA LL Association for 50 bucks and download all forms including leases from their website.

We also weren’t able to have our cell phones out due to “disclosure agreements” The whole thing felt like a waste of time and a scheme.

In addition, speaking with them is generally a waste of time. 

It’s currently setup as a large studio without a kitchen, but we plan to eventually erect a wall to create a bedroom, and install a kitchenette.My question is, knowing how persnickety Portland is with regard to Airbnb, would it be a smarter strategy to rent it out on a longer-term basis to a regular tenant?

I do not have a general contractor yet so I am not quite sure how much to expect as far as the remodel work goes as there are some significant changes I am making, adding sq. ft moving kitchen, bathrooms, exterior walls, removing interior walls, new roof plan etc. in addition to the usual new texture, flooring, paint job etc.Unless the preliminary plan is done, there is no way general contractors can bid on it but at the same time this being my first rodeo I have no clue how much to expect in this circumstances.

I have no argument against @Jaron Wallings advice. 

@Jaron Walling one that I have found the owner is in bankruptcy and the property has been sitting for a while.