I wish to purchase an iMac to share with my son. Can I split the hard drive into 2 partitions and install OS X 10.11 on each partition? I want to ensure that doing this essentially makes it into 2 separate computers and that if one partition got malware or a virus it could not move to the other partition? Also, if my son downloads a 30-day trial version of a software program on his partition, can I still install it on my partition at any time after his trial runs up? Are there any cons or special software needed to do this?