When to consider the networking for multiplayergame?

1: make the standalone features or the basic logic firstly and consider to add networking feature in the end?it can

It is can handle the schedule easily, but may have a huge work to add networking in the end

2: considering the networking and Making the BP or C++ at the same time

It is will work fine in the end, but also will spend a lot of time in prototype design

Can anyone tell me how to organize time or schedule ,thx