You have quite a requirement here, particularly if you're new to Joomla. Honestly, as a person coming from a development background, I believe you're better off writing the code without Joomla.
What are you trying to achieve? Is it fast development with low cost? Is that why you opted for Joomla? Well for what if you're trying to achieve, there are 'paid' plugins. But if you want to do it your self, I guess you're better off writing your own code.
If on the other hand you are a Joomla person, and you have a lot of pages that you (or someone else) will edit using an interface, yes, Joomla is the way to go.
Now, if you want to show your thumbnails on the homepage, there are many plugins. Start with an easy one like sigplus. But, you must know some coding.
Then for payment, I'd advice you to do this:
1. If you're with PayPal or MoneyBookers for example, you can download the plugin from the Joomla site.
2. Then do the simple configuration of entering your email, success page and reject page.
Now you can use the built in core modules to handle registered users and visitors separately. Again, it's easy said than done.
Hope this helps :)
