Will the title company put this property under our LLC name, and won’t be required to legally inform HUD/tax authorities. - will it influence property taxes once we move to conventional loan in 3 yrs? 

Just to add to what has been said here - if the seller described this as a triplex on the sale documents, they might have a legal liability.  

.: I haven't passed this past legal review so for what its worth: Part of my standard requirements for everyone include income is at least 3X rent, minimum credit score, say 640, Clean record and no evictions as well as deposit is paid in full at signing of lease and 1st month rent is paid in full prior to handing over the keys.

The real prohibitive costs come from the legal, compliance, and reporting requirements of registering a security.

It is a separate legal entity.

I am assuming short-term rentals would be legal in the municipality.

With the internet, there aren't really do overs -- most websites have other websites that grab (legally or illegally) information . . . it is pretty impossible to make anything disappear once you put it online.

This is something their screening probably would have caught, or their system would have a legal procedure to deal with it.

Weeks later, it was communicated to us that the underwriter wouldn’t accept the ones signed by only one of us – legally binding for LLCs – and required we send amended copies of leases signed by both of us.

Note that legal and transfer costs are not deductible but can be added to your cost basis.