The seller is working on getting the house classified as habitable again so that I can buy it, but I don't think they will remove the boards from the windows and doors and frankly I would prefer they leave it to help deter squatters.  

Perhaps the answer is to offer to compensate them for the mattress supports, at the end of their lease, provided that they leave these custom built mattress supports when they move.

I understand the appreciation part of it unless you have other source of income to support it ,what will happen if something wrong goes and the appreciation you will only receive when you sell the property and also no vacancy means ,you are going to rent it and forget it for ever and never rent it again which is not true ,you might have to do some renovations ,clean it after somebody leaves and the tenants do not always tell you that they are moving out.

It'll take at least a week to get them served and you should beyond the "please leave" and cash for keys stage at that point.

Purchasing tools, such as an email domain, proves you have skin in the game.

Then a week after closing I decide to leave and rent out both sides.

Is it normally expected for them to have the house clean when they leave or does it all depend on the contract.

@Curtis Tidwell @Brandon BattleI'm hoping the cash for key strategy works and they can just leave amicably.

Someone claiming they are one of only 50 certified SEOs, without any source to evaluate, (not on their website, not on the CEOs Linkedin, nowhere) leaves me with some questions. 

The landlord also knows them better and knows if they are even willing to leave.