My appologies in advance for this huge wall of text, but I give this stuff a lot of thought already, and honestly to keep this as short as I possibly could, this has become a summary of the summary of the summerised summary. I mean, I got each type of ship thought out, goals/guidelines for design of ships, logisitic systems, genetic mods, cities, etc. etc. and that all down to the specific colors and indoor navigation signage.....
If space travel was affordable and viable to you, would you do it? How long? For what purpose?
But If space travel was affordable and viable for me, would I do it? HELL YEAH

That depends, if it's mars and I can't leave it then I got no choice, but if I had my own ship...
If you google robert space industries you will encounter a game in the making called star citizen, If I could wish to have one ship from that game IRL, right now... with a monopoly on that ship and none others out there? I think I would go with the big battleship, assuming that it has a powerful tractorbeam that allows me to tow astroids. I'd use it to tow asteroids into near earth orbit and sell the mining rights to the countries that I trust more than others, I'd sell to the nations I trust in leading the world in the best direction, not the ones who historically shown to be the biggest abusers. The reason I'd go with the big battleship is because there is less chance for me to miss detecting boarding parties and missions to take me out. Cause face it, history shows that one nation cannot stand it if someone is in a significant position of power other then themselves, and he who controlls space controlls the planets orbitals, and he who controlls a planet's orbitals controlls the planet. So I'd need the firepower, scanners and range a battleship offers to keep me safe and prevent a nation from taking my ship from me.
A ship that I'd use to build my own imperium and once getting the scientists aboard that I want, start my own legacy on a planet somewhere. I'd build it's cities all planned out and self sufficient to make them easily defensible against ground assaults, and to be kenetic impact dispercing as possible. The idea is a planet where scientific research is done to increase the survivability of the human race in case of a hostile encounter, and to train a genetically improved human army much like masterchief from Halo ;p I'd try to go there with a large genetic database and sample set to allow for building the people to take this role rather than importing them from earth. The society would get it's own religion, mimiced from earth based religions to make them as resillient to outside influences as possible and to preserve the mission. I'd get experts onboard to build the best possible system for progress towards the mission goals. One of which would always be to be more technologically advanced and in a militairily more advantages position than any other force.
My force would exist of a special forces / space forces orientation with a powerful scientific R&D and logistic support structure. And the planet's location would be kept a secret for as long as physically possible. A force who is not politically intertwined with earth but exists as a shield to turn the tide of battle in case of a hostile encounter, a force of guardians.
If it was practically possible to begin a colony on Mars, would you be interested in living on Mars? What kind of civilisation would you want to build and develop?
Mars is relatively close to earth, so considering current transmission speeds it is already under the political influence of earth based governments. Likely it will first be a frontier world with frontier justice and heavy handed attempts at achieving physical dominance by political entities. whilst the current ISS missions appears to go rather smooth, there is a lot of distrust between the supporting nations, although not as much between the astro and cosmonauts themselves. the fact is however that so called intelligence and security agencies will force the hands of people going on a mars colonisation mission. This will likely lead to the first martian civil war or war of independence at some point.
I would be interested in living on mars however. the thing about being on the frontier is that it will allow you to build a vast capital and legacy for your decendants. Just by laying claim to a vast piece of strategically located land, you can ensure your decendants a good life assuming they are not as stupid as to sell it. As such If I'd go to mars, I'd do everything in my power to find the right piece of such land. My preference would be to find a mountain to hollow out and build my own habitat. The thing about mountains is that they survive most weather effects, so my claim would physically survive a war, a non-direct kinetic impact and the eventual terraforming projects. I'd mke the inside of my habitat as easily defensible as possible to prevent it being taken from me or mine.
As for the society I'd be interested in building for mars... it would have to be forcused on building an independant planetary nation with again a strong scientific and logistical base. If mars contains earth controlled bases or nations, it will lead to it's involvement in the next world war on earth. Mars could become our clean slate. As such I believe it is important to build pre-designed cities that maximise logistics and support a robust with multiple redundancies modular system to allow for easy upgrades and repairs. It could also do everything hardwired from the start to allow for minimal signal leakage and maximum transmittion speeds. If these lines could be made mudular in some fashion too, this would be a great improvement as it could be replaced for new technologies fairly easily. The people on mars would have to be the kind of folk that are good at doing work, research, be self sufficient and have a certain degree of pride as martians rather than terrans or decendants of a terran nation. I'd once again prefer mars to become some kind of fortress world. Because if there is one thing I've learned from history, it is that powers will always seek to influence and control or assimilate others. As such, I'd prefer mars to become a highly independant and advanced planet. Think of it like an alaskan middle of nowhere household, rather than a suburban household in say washington. But then one with the technological advantage and the most streamlined systems in place for education, logistics, healthcare and development. As for the people who go there, I'd prefer them all to be of just one religion, or none at all. If people cannot see themselves as martians first instead of some terran etnicity, then they have no place on mars and should be deported. Mars could not afford anything other than a unified front.
I think for mars, it would be important to prioritise building its own sensor arrays and space defense force. A solid Militairy and Materialistic Independance from earth/terra would have to be it's main priority for it to succeed.
Do you think it is reasonable for Mars to be associated or managed by any company or nation? For example, if it is Space X and Elon Musk that gets us to Mars, should Space X, Elon Musk or whatever team they choose design, manage and govern the colony?
At first if they do a good job, yeah. someone needs to lead, and if it's someone with vision and intelligence that would be the best. However, if the company/person intends to go for a goal other than building an independant martian nation, and simply focuses on exploiting martian resources for the gain of their terran home nation, that person would need to be deposed FAST. Not only is it logistically not profitable to extract resources on mars and transporting them earthbound, the developement of mars would suffer the same fate as the dozens of abandoned gold mining and oil drilling towns in the USA that had nothing other than that going for them. Going down that route would turn Mars in a poor, exploited third world planet resembling some of the poorest places in afrika, where food and water is scarce even when it does not always have to be. I'd have to make sure everyone refers to themselves as Martians rather than Muskies if Elon Musk leads though... I'm sure the terrans would call us muskies either way =_= crap...
I think the planetary government would need to consist of a group of people with the same goal, and expertese in the subject they cover. So like a head of logistics, a head of science, a head of militairy, a head of agriculture, etc. and have them be people leading that industry on the planet for planetary gain rather than individual. Eventually every system will corrupt, but the longer this can be staved off, the better. The meetings would consist of reports on the sector and suggested improvements or solutions for problems, and suggestions for future R&D lines.