What does it give me creation of my own city?

[Madcross]

What does it give me if I buy the creation of my own city, what will be the advantages over competitors, and will there be any at all?

[mauried]

I assume you mean the found a new town option.
This creates a new town in a location where you decide it should go.
It does not mean that the town belongs to you.
The rationale for doing this is usually map dependant and the main reason is generally that the new town will start to build industries like the other towns on the map do.
If industries on the map are small in number and more are needed, this is one way of getting them.
New towns are extremely expensive so its important to consider whether the expense is worth it.