For new builds and some rehabs they are vented but in some conversions or apartment remodels I will opt for the ventless units.

Whenever you add another unit, you essentially have a small apartment building. 

Feel free to reach out to me.

I'm converting one of my apartments to an STR and wanted to know if anyone can point me to an appropriate rental agreement/contract I can use.

Here are a few standout types:Multi-Family Properties:Duplexes, triplexes, and larger apartment buildings are investor favorites.

Quote from @Jimmy Rojas: I live in Arizona and homes here are sky high, youd be lucky to get %6 interest rate, I would be a 1st time home buyer, apart from being 1099 employed would Trumps real estate plans benefit the little guys like me? 

I'm hopeful I'll be able to get my apartment back and not make the same mistakes again. 

Know this:  the #1 reason why landlords fail according to the American Apartment Owners' Association is failure to manage to the lease. 

Over the years, with personal investment alongside investments from family and friends, I’ve been able to build a small portfolio of apartment buildings with a focus on cash flow through strong operations.

@Albert Gallucci as many have pointed out, in the commercial space of 100+ apartment buildings and offices, property classes have some pretty decent industry standards.We started applying these to 1-4 unit properties around 10 years ago, which you can verify on our blogs, because we saw too many newbie investors not properly taking into account things like, neighborhood status, tenant pool, property condition, etc.Unfortunately, there's no industry standard for this, but you can use some basic logic to think your way through your own Classifications.