The colony would start very very dependent on Earth (as seeing as it would need a constant flow of resources to survive). It would likely start with a terraforming project, on either Mars or Venus, to make the planet hospitible. From that it would likely start as an economic endevor (to mine resources that are rarer on earth), and people would colonize, because it is cheapest to live near the resourses rather than commute several million miles to work.

__________________
Set your destination with your heart, get there with your mind.

"The wisest men follow their own direction." - Euripides