The cost for maintaining a site largely depends on how complex the site is to start with. If you have one developed yourself, odds are you will need 10-20 hours a month (sometimes more) for bug fixes, feature enhancements, or general improvements. That's not counting your fixed costs: hosting, domain, etc.

Estimating the initial development gets much harder without a lot more details. You'll want a professional graphics designer do your HTML/CSS layouts and then a web developer to implement the page layouts along with all of the dynamic aspects of your site (logging in, payment processing, etc.). Suffice it to say, initial development is usually the most expensive part of the project.

You might want to look for open-source solutions or a product you can purchase (like WishList) that might have 90-100% of what you're looking for. It will not only get you to market faster, but will vastly reduce your costs.

Depends on what the site is, dude. We run a dating site with about 350 members, and just spend $40/mo on a VPS...

If you need help, PM me.

Well once it is set up correctly, then maintenance should not be an issue. Or maybe I do not understand what you are saying. What type of maintaining are you talking about?

If I were you, I would hook up with the guy in the thread that has the Dating site and runs it on a VPS (Virtual Private Server). Because I have not dove into VPS servers in my career just yet. If you are looking for help setting up the membership aspect of it, then I can help you with that. It may help to start a thread on the S2 Membership plugin for Wordpress.

Wait... Are you even using Wordpress?