Are you intending to run it where stored? If so you need to take the same precautions for any desktop - away from carpeting that will tend to cause fluff in the CPU heatsink when the PC runs; free air flow for cooling.
If you want to run it regularly, you will need power and the ability to run cables out of the storage location to wherever you intend to put the monitor, keyboard and mouse. If you want real portability, a minimal desk on castors would be good so you can wheel it out with monitor etc in place.
My very old PC I kept as a backup on the floor in a storage room with the monitor perched on the back of the tower and keyboard perched on the front of the tower. Operated in situ with mouse on the floor.
Remember that if the PC is totally powered down, the BIOS settings will be entirely dependent on the MB battery. It may run down if PC not used. Copy all the details in your BIOS so you can get it back running by putting in a new battery and re-entering the BIOS settings.
Disconnect power cable to avoid issues with lightning strikes etc. If that is not an issue, better to leave connected (power to PC with PC breaker off) to save the MB battery.
