List building is one of the most vital part of a successful online business. I would always recommend starting your list as soon as you can.
To learn more you can go through the free listing course within the dashboard in OLSP. This will give you basics to get started, they even give you 100 free clicks to get your list growing, when you complete the training.
I have a recent video which gives you more details about the free list building course, watch it here.
As I mention in the video above, this course recommends you use Get Response as your email marketing system and as pointed out this will start costing you money after 30 days, however by using AWeber you have a longer timeframe to build your list before you start paying.
Watch this video here where I go through in more details about the difference between Get Response and AWeber
Once you have your AWeber account follow the video below where I go through step by step to set up your first list.
A couple more blog posts that may help you further