Final answer:
The likely outcome for Doug's application to build a duplex on his residential lot is approval, provided all zoning regulations and requirements have been met according to the municipality's land-use district guidelines which permit 2 dwelling units.
Step-by-step explanation:
If Doug applies to build a duplex on his residential lot, and the land-use district permits 2 dwelling units on the same lot, assuming that all other requirements have been satisfied, the likely outcome from the municipality would be approval. This is because zoning regulations govern land use within a district, and if the regulations allow for a certain number of dwelling units—which in this case is 2—and Doug's proposal complies with this regulation, then the municipality usually has no grounds for rejection.
However, it is also important to consider other factors such as the minimum lot area, front, rear, and side yards, off-street parking, and any specific considerations for areas of historical or cultural significance that might affect the building's design or preserve certain features. Only if Doug's plans comply with these additional requirements as well will his application be successful.