Anyways to answer your questions.
1) A GPU is a fancy way of saying a Video Card. You can purchase one at any computer store. But the better ones are usually located online, or specialty computer stores. Don't go to Best Buy and expect to see a really good Video card sitting on the shelves.
2) A decent card is probably going to cost you $400-$700 each. Due to the questions you are asking, I wouldn't recommend going above 1 card for now, until you know what you are doing. And actually if your planning on spending quite a bit, I would recommend purchasing an ASIC miner, then trying to make a large GPU miner. If you need to ask what a GPU is, you really aren't ready to put together a multi GPU mining rig.
3) Not sure what you mean, but you will need to make sure you have a large enough power supply for your unit. With a 1 GPU unit, a 600 W unit should be enough, once you go bigger, the Power Supply needs will start going up a lot.
4) No idea, but if you know how to do this, you could become a millionaire without needing to mine. Unless you plan on running a cord from your neighbors house to yours to plug in your miner. (PS you better not be my neighbor)
5) I really don't recommend you do any CPU mining. There might be a coin or 2 out there yet that you can CPU mine, but probably not worth it.
6) Yes ASIC mining, or in your case, you might want to look into Cloud mining. A lot of them are questionable. I can recommend the one in my signature or click here:
https://Micro-btc.com/?r=Vivisector999 as I use that one for some extra mining. I think it's legit, but you never can tell. If you click on my link and sign up, you will get a small fraction of a cloud miner as your own, which will mine for you for free. If you want to it to mine faster, you will need to put some money into it though, like I have.
7) That one is very random. Basically the bigger you want to get the more you can potentially make. If you spend $1000 you aren't going to become a millionaire by mining. Mining is more a for the love of mining thing than a big money maker. I can usually make more trading coins in a single trade than I make mining all day. Some spend $20 purchasing some cloud mining. Others spend $100,000 or maybe even a $1 million buying large ASIC miners to actually make some money. With mining it takes money to make money. But only do what you are comfortable with.
8 ) Cool No harm no??? A GPU miner is not really that much different than running a computer in your house. There are at least 2 main factors you need to consider though. Miners suck down a lot of Electricity, so be happy knowing your power bill will go up a lot, or warn your parents if you live at home. The second is Heat. A typical miner throws a lot of heat. if you live in a hot climate and don't have a decent air conditioner or place to put miners where it won't heat your house then I would say do cloud mining or don't bother,
9) Not really sure what you are asking there.
