You are not selling a car here. Selling a website is selling immaterial property.
You must first specify what you are actually selling.
- Domain. You can sell a domain as a brand. In itself it doesn't contain more than the domain name. Probably it is best to transfer the domain ownership within same registrar and then let the new owner to change registrar by himself, since in many cases changing owner and registrar at the same time may cause problems.
- If your site has self-built software, you can sell the source code of it with or without the domain. You could also want to sell just license for the software.
- If your site uses licenced software, you need to check if you are allowed to resell it.
- Concept. For example a webshop. Could include the software or not.
- Hosting is usually contract based. Most likely you can't just give the password away, but the new owner needs to make new contract with the hosting company. Otherwise you would be paying for hosting anothers website. Handing the passwords may also be agaist the contract.
First you need to know what you are willing to sell: just the domain or overall concept. Then you need to know what the buyer is willing to buy, for example will the site be moved to another hosting or not. If it is going to stay as is, you need to know, if it is possible to move the hosting contract to the buyer.