Yes, Google Adwords will bring you extra traffic but only a tiny proportion of those clicks will translate into extra leads and sales so you could end up seriously out of pocket if your landing page is not optimised for conversion. There are also certain keywords that are associated with higher levels of conversion - i.e. they are used by people who are browsing with the intetion of buying as opposed to just window shopping so do your research and find out what they are before you place your ads. That way you stand a much better chance of achieving a return on your investment. So far as your second question is concerned, you can specify a maximum cost per click and set a daily budget so how much you spend is up to you.
Yes, you get instant quality traffic compared to months of doing SEO. But you need to know what you are doing as you can suffer a big loss. Strongly recommended that you get yourself educated about PPC. Maybe $10 a day to test new campaigns, and then once you know which keywords work you can scale up slowly. I spent 4-figure monthly on PPC and my ROI is 100%.
Adwords deliver what they promise - clicks at a price you decide. I typically pay just 10% of headline CPC to get traffic drip fed to my sites - takes longer, but much cheaper. Best way to learn how to get started is using perry Marshall's free guide http://www.perrymarshall.com/
what type of question is this?? Does Adword bring in traffic? Read the Adword page, or google Adwords
ppc will bring in traffic instantaneously. it'll cost anywhere from $0.05 to $10.00 per click, depending on which keywords you use and a whole bunch of other factors.
Of course, it'll bring you traffic, but not targeted traffic until you know what you are doing. Learn the rope and analyze what mistakes you have made. You must have a strategies in place, my friend. This can burn a big hole in your pocket very fast.