At this point merging is closed, and when settlers reopens it will be 1 domain per account unless upgrading. So if you are a mayor, you can buy the county you are in hence upgrading, but you can't buy another settlement of the same tier, nor can you buy outside of the domain where you are placed unless on a separate account and merger would only be available through in-game mechanics after launch.
Why do the nations rage, and the people plot a vain thing? The kings of the earth set themselves, and the rulers take counsel together.
