Rule over an area is either inherited or from a different source that is new. When a person gains his power through inheritance, Machiavelli say it's easier to hold onto one's power in this case because the people are familiar with the prince's family who has ruled over generations. A new principality is either totally new, or it's territory that's been annexed. Machiavelli sees great problems when maintaining control because a ruler must have the support of the native peoples, and he must have powerful people who support him and keep order if the ruler should die.
For the person who rises to power from "a private station", he must have either ability or money, but Machiavelli feels ability is much more important because the ruler shows he is wise and courageous, possessing all the attributes needed to rule successfully. When a prince has these heroic qualities, he's more likely to keep his power, even though it's difficult for him to attain the power. Machiavelli also believes a person who rises to power based on his wealth will have an easy time getting there, but he'll have a more difficult time remaining at the top. When a person rises to power due to the people or the nobles, he should watch out for the nobles who consider themselves equal to the ruler. The prince should get the support of a few of the nobles, and then seek the approval of the people.