Short of hiring a team of developers, there are extensions, plugins and add-ons for the kind of thing you’re asking about.
Do you know what a content management system (CMS) is in reference to websites? If not, a CMS is, as the name implies, a pre-built platform meant to store and serve the content of website. Various developers have created add-ons to these CMSs to give them additional specific capabilities. Thousands of commercial add-ons are available for the more popular CMSs, which are typically LAMP setups (Linux, Apache, MySQL and PHP), as opposed to web applications built around JSP or ASP or whatever…
Here are the four big LAMP-based CMSs you might look into:
I don’t know if anything is available for Magento, although Magento is specifically meant as an e-commerce platform. Joomla would likely be my first choice since it’s a bit more approachable than the more developer-oriented Drupal. Wordpress is doable if you can find the right add-ons, but Wordpress — despite it’s popularity — is a repurposed blogging platform that’s handy to use for less specialized websites.
These add-ons (variously referred to as extensions, components, plugins, etc., by the different CMSs) can usually be found through web searches and searching through the collections for these add-ons associated with the different CMS’s main websites. Don’t get these add-ons confused with themes or template — they’re not the same thing.
What I’d suggest to get you started is to do a Google search on each CMS platform. For example, Joomla marketplace or Joomla classifieds or Drupal classifieds, etc. I could point you to a few specific recommendations, but I don’t know exactly what you’re looking for, and it’s probably best for you to dig into it anyway.
All that said, what you’re proposing is still a huge project that will require extensive amounts of experience to pull off. It will likely require hiring both a developer and a UI/UX designer if you’re not one yourself, which I’m assuming you’re not based on your question.