This is called a drip campaign my friend. Marketing 101. I expect along the way there will be a few emails that contain some info to buy something - a class, another lesson, book, etc. nothing wrong with this and I think it's a nice way for devs to offset time costs associated with free.

Now, for building RESTful JSON apps, it's actually not hard at all. Your two friends in this are:

NSJSONSerialization NSURLSession

Apple has made a lot of progress in his area and, from my experience, where people go wrong is using some other library to handle these tasks. Granted, other libraties are there because someone saw an opportunity to 'simplify' things, but more times than not, they're abused and misused.

My advice, get to know the above classes and separae your your networking and model de/serializing into other parts of your app architecture. Do not shove all this oun a view controller!

Think about clean separation and you'll benefit later down the road. I've built about a dozen json api's and iOS app counterparts and this approach has always worked well.

Good luck!