Without meaning to sound harsh, you really must research this stuff *before* you find yourself in the situation.First thing you need to do is research (via Google) your county and state rental laws.

That may have been them adding value, but regardless it’s a fact of life and a useful thought to keep in mind.

Reliable a d not too expensive.

If you have a W-2 job, 1) you rental income gets added to your income and gets taxed at your marginal rate2) if you have a loss, and your AGI is below 100k, you will get to deduct loss up to 25k against the W-2 income ( this is where the tax saying comes in). 

You can tell a lot by driving down a street or "virtual driving" using Google street view.

You also might want to get a 'ghost' number through something like Google voice to use on those signs to make it difficult for code enforcers to deliver a fine. 

Someone added a layer of 1/4” or 1/2” drywall on top and just caulked it to the baseboard.

If not, please google or search here.  

MLS) then probably no value can be added 2.

Just write an addendum removing the departing party and adding the new tenant.