Hi @Chris H
I'm a broker in Edmond. Without knowing exactly where the property is (or more importantly how it's zoned), this might be a bit of a generic answer. I see you mentioned that the land is unincorporated, so I'm assuming it's outside of city limits so the governing municipality would be the county. There is a big difference in process of Oklahoma county (south of Waterloo) and Logan county (north of Waterloo).
1- If you are building quads or duplexes, there are a few local builders that we know that would love to take on the project.
2 & 3 - These go together. I'm going to assume that the land is unplatted, so survey work and engineering work would need to be done to determine the best fit that also complies with local municipal codes and guidelines. This work would show streets, lots, water mitigation, and utilities easements. With an initial proposal, you can start the process of attempting to get it rezoned. The City of Edmond, for example, does a great job with their city planning and protecting the long term property values, so be prepared to make adjustments to the original plan.
4 - Most of the local builder have contracts that can be used, although we'd always recommend having your attorney review the documents.
Let me know if you have any other questions.