how much to charge sold website hosted in our hosting?

Depends if you are on shared hosting or a good dedi etc.

and then the bandwidth and resources the site uses

if you are stuck, divide your resources by how much you add a % for profit and quote them that and let it slide based on what they use.

Really depends. Are you set up to handle technical problems or are you in a reseller scenario and basically forwarding those request?

Are you in the position to give a client the final answer? Are you at the top of the food chain or are you killing time waiting for their support to be your support?

Say I run private script autoresponders, does your email client pass can spam headers and footers. How many emails can I send an hour?

I have a php membership site that is dependent on Ajax .... it runs on social traffic can you guarantee enough resources to handle the spikes?

I have a v-bulletin forum with several plug-ins ... are you sure you can really guarantee unlimited resources for this site?

I have an article directory that was hand coded and admittedly the code is somewhat clunky ... it gets hacked about once a month ... how long do you keep back-ups of my files? I am the customer ... I don't care if it is my place to do my own back-ups .. host gator holds my files for at least 7 days .. if you piss me off ... can you handle the social media slur campaign?

I run reseller hosting a lot ... I learned a long time ago ... it was better for me to take advantage of the low cost of hosting by using the space for my own sites and leave the true hosting to those that are set up to handle the BS.

But then again, if you are set up to handle all the things a real hosting company does ... it could be a very profitable venture.