Adding a shopping cart into my e-commerce website?

I am opening up my own e-commerce website where I will be selling affordable clothes to the public online, very much like Victoria’s Secrets and ASOS. The problem now is that I don’t have much money to invest into website development and would like to do the whole website myself – inclusive of website development, website maintence, etc.

Can anyone recommend a good website to go to to download any templates? Also, how do I add a shopping cart and include a credit card payment thing? Do I have to approach the bank for approval?

Would be great if anyone of you can enlighten me on the whole process! Thank you!