If you will explore surface/caves long enough there is a chance to find village/mine, protected by some enemies. After killing all monster on map property is yours.
If you conquer mine you will receive some rosources every day, but if it's village you will receive some gold and can recruit one mercenary to help you in battle. You need to pay him every day and gained experiecne will be split.
When you save enough gold you can upgrade mine or village to gain more resources/gold every day. There is no limit in numbers of possessing property.