You actually don't need to install the full client (which has the entire blockchain) but judging by your question I'm guessing you don't know much about bitcoin, in which case I'd advise against mining. Bitcoin mining is now done on ASICS and a basic one will run you upwards of $3,000. Its not unusual for serious miners to have multiple ASICS running in tandem. Unless you are really serious about investing in bitcoin mining and have a solid IT background, I'd steer clear of mining. If you're just looking to put a few hundred bucks into bitcoin, just buy some on Coinbase.
You can't! Well you can but you would have to pay out bags of money for equipment and running costs and get negligible amount back. You are a couple of years too late! If you want Bitcoins why not buy some?
I sent an e-mail to Genitrust and they sent me a ton of information on mining equipment specs, pricing, and networking resources. They really helped me get started in the mining game!
also do i need the 30 - 40 gb database to do so?
