[1000feet]

I can tell you that the parts you described should take a week (full-time) at most for someone who knows what they're doing, not including design. The questions is, do you want to put in the effort to learn everything yourself and piece it together over time, or do you believe in it enough to invest in someone who can do it quickly?

In the later case you'll need to think about it some more and decide exactly how it will work, so you can minimize the work it takes to get it running. You can find people to do it on rentacoder, elance, guru.com, programmermeetdesigner, and other smaller sites. One danger with this is that there's a wide gap between making a site that does what you want and making a good site, and if you don't know the technical stuff it's hard to tell if there's security risks or if the site will break down completely later on.

If you want to do it yourself the first thing is to learn HTML. You'll want to start by putting together basic pages using HTML files (if you hire a designer later on make sure they give you HTML files to avoid extra work). There's plenty of tutorials for this, and it's also easy to learn how to upload them to your host and view them online.

The next step is to learn server-side scripting. Once you understand how to create pages by hand, this will let you have the server generate the pages; for example, you can create a template for a page and then have a script place the right image in it and display comments below. You'll probably want PHP and MySQL tutorials for this, although Ruby on Rails would be another good option that many hosts support. Once again, the work doesn't end when the site appears to do what you want. Try to do unusual things with it (like posting a 100-page comment) even if you don't think anyone else will try and see if the work, and also search for information on web application security (especially SQL injection and cross-site scripting).

For payments, there's several services that can do most of the work for you. Once you sign up their documentation should explain how to write the code in common languages and how to configure them to test transactions without really spending anything. A few examples are paypal merchant services (several levels of integration), authorize.net, 2checkout, and google checkout. Some of them require a merchant account, but with some of the paypal services you can just take payments online and send them to your bank.