Is ASA5520-CSC10-K9 bundle support HA feature set or We have to buy another HA license for the same?
Because I want to buy 2 Nos. of ASA5520-CSC10-K9 for running in HA mode but it's not showing any HA feature set in configuration tools.
If you have ASA5520 in a failover pair and you choose to have a CSC module then, both units should have a CSC module for hardware compatibility.
If one unit's CSC module goes down then the other unit (which is presently active) will take over and the CSC module in it will start to scann the traffic.
Here is the link to configure the CSC module in failover:
There is no failover license in particular for the CSC module. It is same base and the plus license that you always get.