Nothing was in writing yet, so no harm no foul, but owner decided your idea (sell the property) was a good one, and the agent found another buyer, for more money. 

I mean no harm.

These are the folks the rest of the real estate investor community can thank for the SAFE Act and Dodd-Frank, predatory operators went too far and everyone got hammered.It then goes to say that any honest, ethical and lawful real estate investor shouldn't have anything to do with the scam artists in the industry, they cause great harm to the public and in turn to the industry as a whole, They are not heroes of the industry as their gurus and coaches make them out to be or as they proclaim.

i mean if i were a realtor searching for great investment props and came across a great one there would b no harm in taking it for myself thats not unethical to buy some more of my own. so how does that work?

There is no harm in having 10 month leases, or even month to month.

We ask one to leave, but if they refuse, unless they are causing harm, lawfully there is nothing we can do about it.

I also find that (not labeling every smoker, just in general) when someone has a bad habit like that which is knowingly harming themselves, they won't take as good care of my apartment either and often comes along with other bad life habits.

We don’t know any PMCs to recommend in the area mentioned, but since selecting the wrong PMC is usually more harmful than selecting a bad tenant, you might want to read our series about “How to Screen a PMC Better than a Tenant”:https://www.biggerpockets.com/member-blogs/3094/91877-how-to-screen-a-pmc-better-than-a-tenant-part-1-services-and-processesWe recommend you get management contracts from several PMCs and compare the services they cover and, more importantly, what they each DO NOT cover.

Complaints about cleanliness can be very harmful to an STR performance.

Some simple things could be;Adding coin operated washer/dryer (If they don't have them in their units already)Covered parking and adding a monthly charge (Not sure how well they'd like that)Adding standing BBQ pits or maybe some type of play set for kids (Could harm insurance rate)