If I purchase a short term rental, with the intention of maximizing only year 1 tax benefits do I have to have the STR in service for a FULL year from when it is placed in service, or can it be less than a calendar year? 

Part of my intentions are to clean up the properties and run a more respectable operation.

I've purchased about 30 ppties this way and NONE of them have ever had intentional damage, although I once evicted a tenant that did about $1,000 damage intentionally and I saw a neighbor take a chainsaw to about 20 feet of load bearing wall during an ugly divorce.all cash

Your choice to spin it around to appear that your intention was simply to help, is disingenuous.

Also, I have heard its a good idea to be up front with sellers about your intentions.

I intentionally will sit there when there is a pause.

IMO, It's a sham transaction to act in the same capacity as a listing agent for a fee, a net listing, where the seller says I want this price and anything you get above that price, you can have as your commission (which is illegal in Mo.).SInce there is never an intent by the investor to excute the option or purchase the property, and the only intent is to find a buyer to turn back over to the seller, it's obvious it qualifies as a sham transaction.

This is why you tell the sellers upfront what your intentions are.

It must state some language to the affect that the property is being purchased by an investor with the intent to sell for a profit.There should be no difference in the disclosure method between using the option contract and the land trust.

If the house was not built with the intention of two separate units, there will not be proper fire separation between the levels - this you will have to rectify to make a legal duplex.