Why asteroids? Mining a near asteroid is the cheapest and quickest way to go. It costs less than the moon and the rewards are higher and more immediate.  Asteroids are rich in valuable resources Asteroidal materials are useful for propulsion, building material, life support, agriculture, metallurgy, semiconductors, precious and strategic metals, to manufacture structural materials, for solar photovoltaic arrays which could be used to power space habitats and/or lunar habitats, space tourist facilitation / accomodations (ie. orbiting hotels), pharmaceuticals, semiconductors, ultra-pure crystals, for radiation shielding. Precious metals and semiconducting elements in iron meteorites are found in relatively large concentrations compared to Earth sources. It may be possible to extract up to 187 parts per million(ppm) of precious metals. It has also become clear that the NEAs are much more rich in desired raw materials than the Moon. There are just a few places on earth where ores are concentrated enough to make mining worthwhile - the good stuff sunk to the earth's core long ago.  With planets and earth's moon, lighterweight minerals with oxygen and silicon rise to the surface to form the crust and upper mantle, whereas the heavier minerals and the substances which do not bond with silicon or oxygen (such as gold, platinum, and others, including heavy radioactive heat sources) mostly sink to the core. Iron exists on the surface of the earth bonded to oxygen, silicon and sulfur, but never in its free form. With asteroids, you get free ore. Good (pure, free) ore requires very little processing. About half the world's nickel comes from a mining area in Canada called the Sudbury Astrobleme where a giant asteroid impacted Earth long ago. The Sudbury Astrobleme also produces platinum group metals which are separated from the nickel. "... a two-kilometer-wide asteroid holds more metal than all the ore mined on Earth since the beginning of civilization." --usra.edu (pdf) Compare to the moon "..easier target to reach logistically than the moon.. takes considerably less energy to land on and take off from an asteroid than it does the moon.. lack of gravity also makes the mining process much easier.." --192.211.16.13/curricular "... there are some (NEAs) for which it would be easier to effect a spacecraft rendezvous and landing than it would for the moon ..." --aas.org (doc) "some asteroids are easier to get to from the Earth than the Moon is" --ari.net "... Some of them would be easier to reach and return materials from than our Moon. .." --floridatoday "... even easier to get to than our own moon. " --iinc.com "Many NEA are easier to get to than the Moon" --lpi.usra.edu (pdf) "Jet Propulsion Laboratory scientist Donald Yeomans said: 'Some asteroids are far easier to land on than the Moon itself.. '" --nasaexplores (pdf) "Some NEOs are easier to get to than the Moon." --planetary.org "In terms of rocketry, they are easier to reach than the Moon." --sciencenet.org "...they have low delta-V requirements, making some easier to get to than the Moon." --seds.org "Some half a million asteroids 100 yards across or larger orbit the Sun along paths that cross or come close to the orbit of the Earth. In principle, it is easier to reach about 100,000 of these "Near Earth Asteroids" and return a payload to the Earth than it is to return the same payload from the Moon." --space.com Free metal concentrations in stony meteorites are about 20%, compared to a few hundred ppm in the lunar regolith. M-type asteroids are about 99% metal. C-type asteroids have 5% to 20% water. The lunar surface, by contrast, has no native water. Solar wind implantation of hydrogen on the lunar surface offers up to about 50 ppm hydrogen, which, if fully released and fully converted into water, would optimistically give the lunar surface about 0.045% water. Overall, the lunar surface is volatile-poor and metal-poor.