Currently we don't even have money to send crew to Mars. Estimates by some experts have put the price tag for a Mars trip in the hundreds of billions of dollars. Even if we could get there right now we must terraform it first because Mars is a geologically dead planet. While Mars has plenty of volcanoes and geological evidence that there was tectonic activity at some point in its history, that's not the case anymore. There is no air pressure to hold in water and Mars suffers from the lack of a magnetic field that would shield it from harmful solar winds. Any effort to process Mars into a livable planet (i.e. terraform) would have to take all these factors into account. Perhaps it would be possible to jumpstart the atmosphere by turning the carbon dioxide-rich air into oxygen much the way plants on Earth clean our air. But Mars still wouldn't have a magnetic field. Without a magnetic shield for protection, extreme waves of solar radiation strip away the Martian atmosphere, thus subjecting humans to lethal doses of radiation. Evidence suggests the polar ice caps have the remnants of a magnetic shield and are safe from the extreme solar radiation.
It doesn't cost hundreds of billions, they are realistic plans that could get a crew for a couple of billions divided on a decade or two of the program (so that's a couple of hundrends millions of budget a year), (example Dr Zubrin plan), which is nothing compared to the money spent on other useless things, example F22 Raptor, LCS ect ect, as for the in Mars problems and challenges I believe they were discussed in this or in another article, getting there and starting to do scientific research and setting bigger settlement is a start, terraforming is something for the far future, but everything should start with a step, and if we are too afraid to take that initiative it's not going to happen ever