How to purchase a node?

Excuse me, I'm quite new to the world of cryptocurrency and I've been hearing a lot about nodes lately. Could you please elaborate on the process of purchasing a node? I understand it's a crucial aspect of maintaining the decentralization and security of blockchain networks, but I'm not quite sure where to start. Do I need to have a certain level of technical expertise? Are there any prerequisites or steps I should follow before making a purchase? I'd appreciate any guidance you can provide on this matter.