But before we can do that, we would need to find ways of adapting to these new conditions. I mean the humans who got to Mars would have very little sunlight, which would affect their bodies due to the vitamins. And also the lowered gravity would most likely cause problems with the human body, such as muscle and bone loss.
I'm not certain on the next point, so feel free to correct me if I am wrong, but doesn't Mars have no atmosphere? And if so how would we get enough Oxygen to live, grow plants etc?
We have lights that isn't a problem,
Muscle and bone loss is not a problem, unless you want to come back to earth.
There really isn't any problems other than money and will power.
Mars does have an atmosphere, but a lot thinner than ours and little oxygen. You would have to have greenhouses to provide an atmosphere and to produce oxygen.