SSG5 ist EOL and ideal for some playing at home with them, you can get them on ebay for 20$ already.
Does anybody know how to get a NSRP Cluster license for free?
Licenses like the ssg-5-elu are only sold new or tied to a specific hardware serial number.
So you would need to purchase a used unit with the license already enabled or get a new unactivated license key to activate on the Juniper license tool.
Not only that, it also needs an unlimited user license.