How to set up a website to allow people to login and stuff after buying something from form my site and have diffrent buy options and diffrent membership levels and they can up grade there membership to a higher level at a later time, ect and they can make a s/n for a forum at the time of sign up / purchase something, ect....

login and "stuff" means ???

But answer your question:

You get the backend written, have a frontend designed, host it and promote it.

But before you even start:

You need a precise idea of what you want. Having the wooly and vague description you have given us is NOT the way to get real useful advice.

But there are also some professional template websites which offer these kind of service free of charge!

Originally Posted by DemonGodKid

How to set up a website to allow people to login and stuff after buying something from form my site and have diffrent buy options and diffrent membership levels and they can up grade there membership to a higher level at a later time, ect and they can make a s/n for a forum at the time of sign up / purchase something, ect....

I'm not really sure I (nor anyone else) fully grabbed the meaning of your post, but from what I GATHER, you need a CMS. What I don't know is if you're wanting to develop one yourself or use one that already exists. You'll hear a lot from myself and others here on this forum about the wonders of WordPress, which will do (I THINK) everything you mentioned in your post, as will Joomla. If you want to develop it yourself, if you're not well versed in PHP, I'd start getting that way....and keep starting for awhile.

Hope this helps, if even a little.

Planning the path your visitors are going to take on your site before building it a) makes your site is easier to navigate for visitors. VERY true. Pretend your visitor has a broken attention span and you have to help them!