I recall reading that they do intend to create structures which would be used for crops and things, and to make it sustainable.
In regards to the people chosen: You guys are correct, Mars One didn't require special qualifications, but I beleive they did this because wanted as many applications as they could get (you had to pay to apply); chances are they will pick at least some applicants for having useful qualifications.
As for it being a hoax: I honestly am not sure what to say to that. It seems like somebody would have figured it out by now, cuz to some people going to Mars is kind of a big deal.
There have been some interesting updates lately. For one thing, they didn't get nearly as many applications as they expected, but they plan to continue in spite of missing out on some funding (big surprise, not that many people were willing to live on Mars for the rest of their lives). They are currently narrowing down their selection of people.
Fun fact: part of the application asked people to describe their sense of humor.