The wire is over 2 ft underground, and other safety measures. They have to worry about foxes, bobcats, hawks and coyotes. They let the chickens out if they are home, and keep an eye on them, but they have had losses. If I'm helping when they are gone, I don't let the chickens out. I would hate for anything to happen to them.
When my daughter decided to get a flock, she imagined it'd become a way for her kids to make some money. When we saw the coop, my husband and I thought they'd have to sell a lot of eggs before they saw a profit. 
The flock has never made money, but they enjoy fresh eggs most of the year. The flock is entetaining, too. This is the 4th or 5th generation of birds. There is a rooster, sometimes more than one, and the interplay is interesting, to say the least.
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