Ok, its the question almost everyone thinks at one point in time but it's also the question almost everybody is afraid to answer :
How will space colonization ever be financially successful ?
Is there gold on the Moon ?
Can we ever trade ?
and if there are no Green Aliens who want to trade with us then how do we get the dollars, the euros or the yen flowing out of Mars ?

Let's imagine for a second its 2095 or maybe its 2208 LOL does the date even matter ?
What does matter is that we have started to colonize the solar system and have thoughts on going beyond Mars. Maybe the United States has been massively successful, building new domes on Mars. The United States found a new form of ground breaking transport and a first and second generation of U.S citizens have now been born and living on Mars, these colonies now hold thousands of people. Maybe it was the Russians and the Chinese who colonized the Moon and established a neo-socialist government. Perhaps it was the Europeans, or Japanese who built the first research station on Ganymede, a research station supported by a small village of astronauts. What was the village called ? New-Washinton ? New-Calcutta ? does any of it matter ?
Maybe not because our first priority in this thread is
Money
- $ £ ¥ € - take your pick because whether or not we use Martian dollars or Martain Euros is not of immediate importance.

What is important is getting the money pipes to flow

Some of my zany and not so zany thoughts

Gold Rush & Lunar minerals
Maybe we could trade minerals with each other, somebody also point out to me there could be lots of 'oil' on Titan but I still have doubts about something like this being financially successful. On the Moon with no atmosphere perhaps it is easier to transport materials back to earth, maybe they could build a giant rail gun shooting commodities from the heavens back to a rendezvous point at Earth. Maybe we will be exploring this idea of beaming microwave energy from the Moon down to Earth ? The problem I foresee with some of this, is I imagine most of the trade will be one way and that we on Earth will be sitting on the real goldmine, literally charging the colonists astronomical prices for essentials like water, pharmaceutical medicines etc or will the space truckers dominate this market ?

Vilos Cohaagen Private Limited Company
Allow a group of megalomaniacs to run Mars like their own company, it would attract a small select group of private investors giving Bill Gates, Abramovich, Li Yanhing Robin, Donald Trump, Jim Walton, or the CEO of Halliburton indirect control of Mars and its people. Eventually these Megalomaniacs might surrender their control and allow the company to float giving individuals freedom to invest in a public company with shares. Of course there's going to be something like a 14 minute delay so expect stock Exchange delays just like in the early days of Dutch, British and American stock exchanges.

Mars Com sats & 3D TV Entertainment
Investing in the flow of information, maybe your broker will tell you AT&T will be making a huge buck this quarter as the public gets charged outrageous prices for making that call home during this holiday season. Maybe will all be watching celebrity island survivor on Mars or maybe Jackie Chan and Sylvestre Stallone will be making Rambo-9 on Mars.

Long term investments R & D
This area could be massive it could also be a financial dead end. It means people putting money into something that will not show immediate profit. Maybe an investment in capital, maybe its an investment in a orbital research center and a future breakthrough in technological change. Maybe money invested in the designs of new super instruments won't bring instant profit but in the long term will bring super bucks, health, energy etc will see long term productivity benefits.

High class Tourism destination
RutanBranson, have set up their own super company, they have teamed up with their competitor Sergei Ltd and now have exclusive control of the high class destinations the solar system has to offer. Area-502 and the Mosque-of-Elvis have now replaced the MartianPyramids as the top choice destination for Tourists. Analysts forecast a rise in luxury retirement destinations on Mercury.

Dark Market Deals
Colonies go out of Earth control too fast, the territories become lawless or become dominated by gambling, stolen technology sales. The people of Mars live in an anarchist capitalo syndic society but dominated by a higher class. Authoritarians rule at the top, the new Martain king is a direct genetic descendant of Yuri Gagarin or Alan Shepard. The people adore him but unfortunately the trade in this society is dominated by high class narcotics, weaponry, slavery or prostitution

Soprano waste management
Elettronica-nose Soprano operates a space station at Venus. He deals with getting rid of all the undesirable stuff we need buried, hazardous toxic materials, dumping of the world's chemical weapons left after the third coldwar, space junk, waste from nuclear power plants, undesirable anti-matter debris. You need it trashed ? Mr Soprano can do it for you confidentially at his Venusian station.

2097 ? a typical business headline might report something like this
Energy - Shares in lunar energy climbed today as Moon output soared and forecasters predict higher output from Moonbase-One and fewer solar storms for the next year.
Travel- Stocks in RutanBranson travel remained flat but analysts recommend long term investment with the RutanBranson company investing in luxury Northrop liners as well as the cheaper low cost antonov space fliers.
Titan Oil - Shares plummeted today as PowerPlant-2 went offline due to a dormant Cryo volcano suddenly erupting in Xanadu. There are also long term concerns for Martian production at Hellas Planitia as the political independence movements gather strength, Titan Oil has been heavily investing in Mars these past months due to its proximity to planet Earth. Analysts predict a weaker fourth quarter and the price of gasoline to soar on Mars.

Your thoughts ?