What's the cost to set up a good mining rig?,

I want to make extra income through the bitcoins mining, but since i am new in this filed i would like to know some points, What’s the cost to set up a good mining rig?, and how long it take to mine bitcoins

You can get a good mining rig for about $15k. How long? Depends of the rig.

With a good rig, about a month.