Hopefully by now you have a couple of thousand Sims inhabiting your City and your monthly income is now turning green, depending upon how much debt you have taken on, it will turn green straight away, or after a few thousand sims have moved in. So, with the cash coming in and demand high for your RCI zones, you can start to lay some more roads and zone up some more blocks.
I've opted to fill in these areas with large blocks, as in the image below as I know I can easily split them up later on.
Zoning up more roads
your income may be green now, but it won't be long until you are spending big again and that takes us nicely to the next phase of the game. Adding social and civic services.