I read somewhere that the first mission we send to colonize outside the solar system will arrive to (hopefully) find a thriving civilization. The point being that in the time it takes the first mission to travel there, we will develop newer and much faster methods of travel.
IMO, we could have a colony on the moon in my lifetime, and probably Mars. But at what cost? 100x what our grandkids could do it for? 10,000x? Since Congress is involved, any number I come up with is probably low.
Speaking of Congress, I guess it really doesn't matter how much it would cost, as they have no Constitutional justification for any of this.