by millsyboy
You probably understand correctly. Once you have a building it doesn't make any difference how you got it.The main differences between buying and building are:
* You can't build a building that has already been built (eg by the town).
* You can buy as many buildings and ships as you can afford on your turn, but you're limited by the construction building you've chosen as to how many buildings you can build on your turn.
If you understand all that already then you've got a good grasp of the rules.