Recommendations for Mobile App Business Database Infrastructure

My friend's are discussing starting a business venture. It will consist of a web site and mobile app storefront. But we are not sure what kind of hosts and database technology is out there.

Being totally generic here, the customers would create log ins and we would want to capture their preferences, sales info, and allow them to collaborate, set up appointments with one another, and search various rss feeds, pull data from web crawling other sites (maybe), and from what we would personally enter in. Basically something that very similar to what Expert Exchange can do but to a different type of crowd.

We know we would not want to own the hardware since that would be far too much overhead while we are struggling to start up. What are some reasonable powerful and reasonably priced solutions to our informational needs. We know we will have to hire programmers, etc eventually, but that is not easy when you do not know what to ask for really:)