Hardware requirements to start mining.
GPU: It's up to you to choose what graphics card you want to mine with. Do your homework. How much is it. How much power does it need. How fast is it in terms of its hash rate. The GPU must have at least 2GB of memory, AMD cards are best to use and AMD GPU driver 15.12. This Mining Hardware Comparison list is very helpful. http://62.212.74.86/~mining/list/
If you want a custom rom (Higher hash, lower power), you can contact Heliox
For example: RX 480 8G Samsung: 32+Mh ETH, RX 470 4G Hynix: 31+Mh ETH
Motherboard: You'll need a motherboard that has enough PCIe x16 and PCIe x1 slots to support the ammout of graphics cards you plan on using in your rig. The Asrock H81 Pro BTC and Asrock H97 Anniversary, are both good boards to use, they are relatively cheap and they can support 6 graphics cards with 1 PCIe x16 slot and 5 PCIe x1 slot. And you will need to buy a power button, obviously to turn on your rig.
Riser Cables: To use the PCIe x1 slots on your motherboard, will need to buy PCIe x1 to x16 riser card extender cables, it can also be used on the PCIe x16 slot. It's also great to give your cards some space from each other. I would recommend buying 1 or 2 extra ones, because sometimes you'll get one that doesn't work.
CPU: You'll want to buy a CPU that fits your motherboard. If you go with the Asrock H81 Pro BTC or Asrock H97 Anniversary, the Intel Celeron G1820 or G1840 works just fine for it.
Power Supply: You'll need to calculate how much power you need. For example, I have a 6 card AMD R7 370 rig, each card uses 110watts of power for a total of 660watts, and the rest of the rig uses about 200watts. So knowing this rig will need 860watts of power, I went with a good 1000watt power supply that came will all the necessary cables.
Hard Drive: A 60GB hard drive is all you need, and you can find a small solid state drive now for a good price.
RAM: A minimum of 4GB of RAM.
You'll also need to buy a keyboard, mouse, monitor, and its best to use an Ethernet connection not WIFI. You may temporarily need an optical drive, to install your drivers and Operating System. If you can do all that with a flash drive, that's great too.
Mining
In this link from Nanopool.org, http://eth.nanopool.org/help, you'll find 3 mining clients you can easily download and configure to start mining. Claymore Dual Miner, Genoil Miner, and EthMiner.
For example. I use Ethminer and I point it to nanopool, so I edited the start.bat file so it looks like this:
setx GPU_FORCE_64BIT_PTR 0
setx GPU_MAX_HEAP_SIZE 100
setx GPU_USE_SYNC_OBJECTS 1
setx GPU_MAX_ALLOC_PERCENT 100
setx GPU_SINGLE_ALLOC_PERCENT 100
ethminer -M -G -F http://eth-us-east1.nanopool.org:8888/YOUR_WALLET/YOUR_WORKER_NAME
Then all you have to do is just run the bat file and you're mining away.
You should know where your DAG file is, because if you don't keep an eye on it, your hard drive may quickly fill up. You only need the 2 most recent DAG files so it's OK to delete any older ones, but sometimes you'll have to delete all of them. For me, I just had to search for the folder "Ethash" and put a shortcut of it on the desktop.
Also some helpful tips.
Set your rig to turn on when power is connected, AND set your miner to run on startup. Just google run on startup. It's a must and you'll love it when your power goes out and you're not home. When your power comes back on, your rig will turn on and start mining again.
Use a remote desktop. I use Google Chrome Remote Desktop, and I set it up on all my rigs. From my phone or another computer, I can control any of my rigs and keep an eye on them.