Building a Miner!

If im going to start mining. What type of computer do i need.
Should i have good CPU or GPU or what'? ...

GPU I guess is the best solution. Atleast that's what I heard from everywhere. Another possibility would be to buy a miner from a provider of machines that are made for mining.
Of course the costs are not the lowest, but if your electricity costs are not that high where you live, it could be profitable. But for this also calculators exist in the internet.