Dedicated server - other games required?

Quick question:
I have an extra computer I decided to set up as a dedicated server. It has hl2 and gmod installed on a new steam account.
Do I need to buy cs:source, hl2:ep1 and all the other ones for those items to be spawnable when playing on the server?

You don’t need any games.
Visit the gmod dedicated server setup wiki and follow the instructions.
Srcds is the answer.