How do I get a new NPC?

I'm curious about acquiring a new NPC (Non-Player Character) in a game. Could you elaborate on the process and steps I need to take to successfully obtain one? Are there any prerequisites or specific tasks I must complete? Additionally, are there any costs associated with acquiring a new NPC, and if so, what are they? I'm eager to expand my team and explore new possibilities, so I'm looking forward to your insights.