Ok, say you were thinking about starting a web-hosting business. The customer demand is there; you'll be serving a niche market, where customer's will be using web-enabled applications to access HUGE databases (10-500GB) shared amongst scattered users. Reliability is a must; some customers will need the data the most in periods of natural disasters. Most access will be password-protected, some data will be sensitive and need to be quite secure, and the applications in question do everything server-side.

I know NOTHING about web hosting, except that there is a demand for the service in this niche, there's money to be made, and I've been told to learn...quick.

Feel free to assume I know nothing, and start at the beginning.

Thanks in advance.