Membership Website with cash accounts

I have been looking at lots of different membership plugins but none are exactly what im looking for.

What i need to do is setup a website that has different subscription levels which grants access to different parts of the website.

I also need to setup a pay per post option. Just publishing a small amount of information into the post, if people are interested then they pay for the rest.

This seems easy enough to do with the majority of membership plugins that ive looked at.

My problem is that im going to be publishing lots and lots of posts, very small posts with valuable information.

I dont want the customer to have to pay for the post their and then as it will take up to much time. Id like them to confirm the purchase and then to settle up later. This purchase would then be logged in their own personal account on the site where they can check how many posts they have purchased and what they owe at the end of the day.

Ideally it would be beneficial if they could load their account with money and every time they purchase a post its deducted from their account.

Anyone done anything like this before? or got any suggestions please let me know

Thanks