I know there is a lot of threads about installing but none that talk in depth about portable A/C units...Backstory: I purchased a 3 bed, 2 bath duplex in Baraboo, WI which rents for $995.

Not only can I offer guests amenities like a pool/spa/sauna without personally have to deal with upkeep, but we have an onsite manager to deal with problem tenants and even let guests in if they lock themselves out, etc.

Best thing to do is pay a little more than a window unit and buy a portable A/C & Heating unit on wheels that you can roll around and put in your rentals temporality when A/C goes out that you can have an use for the next 20 yrs.

Some of my tenants bring portable ones.I wouldn't want to be without a dishwasher, but recently on a trip we stayed with family who didn't have one.  

Colorado has made a similar move, allowing "portable tenant screenings". 

For example, I am going to provide my tenants 2 window AC units, free parking, free storage, and some other amenities that they can include in their lease if they wish.One other option I am thinking about including is a portable dishwasher since these units do not have them.  

Debated pairing them with wood burning saunas.

@Aleksander Dabrowski As you move forward a word to the wise depending on what configuration of rentals you end up with put in a ban on portable washing machines and dishwashers on all floors that have a floor underneath them.

I keep a portable AC (or 2) in storage at my places and whip them out during emergencies for guests. 

I would buy and keep in reserve one of the portable units on wheels...