Venus is closer to Earth with shorter transfer times and tons of solar energy. Unfortunately, its atmosphere at the surface is horrifically tremendously high pressure (comparable to a depth of a kilometer in Earth's oceans) and unimaginably hot (nearly 900 degrees Fahrenheit or over 450 Celsius). Its gravity is closer to that of Earth, which would take more rocket fuel to launch a return flight, but would also probably be better in the long term for human physiology.
A way around most of the problems would be to keep humans off the surface and instead house them in airships or ultimately in floating cities.
It would not be possible for people even to make brief visits to the surface, so mining would be out (barring robotic machines able to withstand the staggering heat and pressure). Almost everything would have to be brought from Earth, though an asteroid could conceivably be mined in orbit. The following video describes some of this:
For more on the concept, see
- NASA's description of its HAVOC proposal for flying humans to and from Venus and housing them there in airships.
- "The Surprisingly Strong Case for Colonizing Venus" by James McGirk, with links to other resources.
- Wikipedia's article on Venus colonization.
- "NASA scientists want to colonize Venus with giant floating cities" by Adam Epstein.