So let's find out if we can survive there longterm. Send volunteers. I'd go and I don't think there would be a problem finding many qualified colonists. There is water on Mars, in huge quantities. The atmospheric pressure is highest at the bottom of the canyons and liquid surface water has been seen there. So a habitat could be just a pressurized tent in a canyon. Make it of a material that can pass solar except for UV and not re-emit infrared. Extra heat will have to come from somewhere.... maybe a micro nuclear reactor or large solar panel field. Start agriculture under tent cover immediately. There is plenty of CO2 the atmosphere and the plants will make oxygen. So will electrolysis of water. Weed and disease free agriculture would be far more efficient than Earth agriculture.... Look, I grew up in the 1960s in Huntsville, Alabama. NASA was a shirtsleeves engineering group that got stuff done. It doesn't have to cost a fortune, and even if it did, it would be worth it to save humanity.