I'm working on a tower defense game, thinking about making it multiplayer, is it easier to start the code from scratch with multiplayer in mind or is it easy enough to take what I have and adjust it for MP?

Also if I start over I may use UE5 this time if that matters. And what’s a good resource or specific youtube channel that’s good to start learning MP code with?

It’s generally better to implement MP as you build. You can iterate back through your code and make it MP, but that’s usually twice the work. Single player flow logic just doesn’t work for networked games.

Also, make sure when you create your project that it is a C++ project if there’s even a remote possibility that you’ll run dedicated servers. You can still do everything in Blueprint. But you’ll want your build to be C++.

As far as jumping to UE5…My opinion is to wait. Start in 4.27, then update to 5.1 when it’s ready. 5.0EA isn’t even remotely stable enough to consider. So many things unfinished, or unsupported that cause issues.