In terms of where to start. You might check out our library of Watch Me Build videos. Some are specific to residential development, while others will provide you ideas for the various components of the model you intend to build:
In terms of phasing. Spencer generally models phases separately if the capital structure is different between phases. He includes the option to model a 2nd phase in his Residential Land Development model, but with the assumption that the capital structure is consistent between the two phases.
May I suggest you consider joining Spencer and Michael’s real estate financial modeling Accelerator? The program is specifically intended to teach you to build complex real estate financial models from scratch, and would be a great resource for you as you work on this project. It would also give you the ability to interface directly with the guys on your specific model via the Accelerator forums. You can read more about the program here: