Hiring can be "you get what you pay for" or it can make no difference, sometimes a fresh out of school can be the best to hire or could turn out to be a spoiled kid still living with the parents who doesn't have to work, but if your hiring skills are sharp and you know what to look for, you can get lucky, and find one trying to make a good go at a careerer.
Watch for the signs that they enjoy what their doing, these employees will whine less and will strive more to doing a good job (also helps if you try to make their employment enjoyable)
Generally 30 days is enough time to see if a person will work out, after this they should be brought up to a pay scale that would reflect their skills, its ok to have a starting pay that seems low, but shouldn't last longer then the 30 days, and always let them know that if they get past the 30 days they will be given a raise or you might scare a good employee away. this also lowers your hiring cost.