how to make a website?

[Jake]

Yea it's far from a sure thing, competing with Ebay is a technical as well as a business challenge. The easiest sort of site to start with are passive information sites like a blog, which can earn some advertising revenue if it attracts a lot of viewers. Creating a site catering primarily to one campus would pre-limit the growth potential (though Facebook grew one school at a time at first)

A web search for "ebay clone script" or marketplace web site script, should turn up some preprogrammed web site templates costing perhaps $100, you still need someone with web site development experience to install and customize such a site script, you can probably find starving computer geeks on campus who work cheap, alternatively there are countless oversees workers who work for a relatively small amount at marketplaces like elance.com, odesk.com, vworker.com who could do the installation and perhaps act as webmaster.
This nice list of such scripts includes Wordpress themes, wordpress is a blog platform adaptable to other applications that reduces the amount of coding required, it's used in some 17% of the top 1 million sites/ http://www.scriptcopy.com/ebay-clone-script/

A small local focused business like you are thinking of might be more successful if you copied the "I sold it on ebay" store concept, where you act as a middleman, accepting merchandise and taking care of the process of listing it on Ebay for a fee (Between ebay and the store fees, people end up making less than the service fees)