Just got my A500 and was about to fire it up for testing

[TjLaZer]

Yes the mouse plugs into one of the ports on the back.  (Back left) This model does not use a Kickstart disk.  Kickstart is in ROM.  Just hook it up to a TV using the onboard mono RCA Video port or the composite port on the external video modulator if you have it.  You will need a bootable workbench disk to use the OS.  Most Hard Drives for the 500 are side car external boxes.  There were some internal models made that could be mounted internally.  They used laptop IDE 2.5" hard drives, but these are rare and hard to come by.

[TjLaZer]

@irishmike

Check eBay for a Commodore monitor.  Models like 1080, 1084, 1950, 1960, 2002 will work great.  I have a couple spares here myself.

Also the C64 is the best selling computer of all time.  The Amiga 500 never came close.  Though it was the best selling Amiga model.

If you want a HD just get a used 2000.  Might cost less than a sidecar drive for the 500.