Once a month I backup my Dropbox Account onto a portable drive.

Many investors use "Simply Safe" it is a portable alarm you can move from property to property. 

If not, can you purchase a window or portable AC unit from the hardware store then ask the tenants if they can use this so that you can save money to replace the AC unit in winter.

Or if all you need is the printer plus a network hub with a USB port or similar.This is mostly for people who work with a portable and want to roam the house.

You might get more out of adding a portable crib.

they do make portable tanks, but not ideal. 

Done.FWIW, I'd say a quarter of my tenants end up buying a new fridge, or adding a window or portable A/C unit, or whatever their personal preferences are ... and 80% of the time those people want to leave it when they move out.

Appraisals are not portable in Conventional financing, so to the bank you only have one.

An old property manager of mine had heard of a portable security system that you could take from rental to rental and pay a small monthly fee for monitoring.However, he can't remember what it was.  

If you ask the average person if its possible to build real estate as a portable career they would tell you no.