About 2 months ago another post on this base subject came up.  

I recommend you print, study, and highlight the HUD guide: https://www.hud.gov/sites/dfiles/PA/documents/HUDAsstAnimalN...You should also check with a local HUD office to see if they have any additional guidance they can provide you.Keep in mind, not everyone is subject to Fair Housing requirements and you may be exempt from allowing the ESA! 

It is much more hands on and dependent upon some sort of subject matter expertise.

Going the DSCR route will also not work since he will be subject to a PPP at the time of refinancing into a primary loan.Putting a tenant there for a year and then anticipating to move in after a year may not also work out depending on the states Laws regarding this. 

Revisiting the subject of financing for vacation home/vacation rentals/STR's.  10% down is still an option without having to pay points.  

So long as each LLC does not own more than two residential dwelling properties, or more than four dwelling units total, the LLC may require two month’s rent as security deposit.Although elsewhere I have expressed the opinion that placing each rental unit into its own LLC is maybe not necessary for limiting liability, if an investor is subject to the new security deposit limitations, the idea of limiting the number of dwelling units in any LLC to four rental units, now has an added benefit of allowing the LLC to require higher security deposits.Below is the pertinent portion of the statute:(4) (A) Notwithstanding paragraph (1), a landlord may not demand or receive security, however denominated, in an amount or value in excess of an amount equal to two months’ rent, in addition to any rent for the first month paid on or before initial occupancy if the landlord meets both of the following requirements:(i) The landlord is a natural person or a limited liability company in which all members are natural persons.

They can't be vague and are specifically designed not to be left open to the subjective interpretation of a fact finder. 

Letting someone else’s (manager) subjective feelings decide your financial fate vs. your fate being determined by your drive.

Ideally, the seller has no existing lien balances against the subject property, so that the down payment (less expenses and commissions) goes directly to their bank account.

If you are financing the initial purchase, you will probably be subject to a seasoning period where you won't be able to refinance.