I have facebook account of 7K now I am unable to maintain it. One of my friends asked me to sell it for some bucks. Can I sell him or leave alone to the page editors.
Yes, it might be illegal but it is not clearly specified on the Facebook TOS but it is against the Facebook TOS. If you sell your page for gain some money then it will definitely a risk for you if you inform Facebook before selling group, page or account, so might be they allow you to sell but Facebook won't allow you for the same. And there is no benefit to selling your page to someone because your followers believe on you and like your posts so how they can like something different on the pages that actually not related to the actual one as it was before. You can read Facebook TOS here. Read the point 9 in section 4.
Although laws change between countries I am confident that selling social media accounts is not illegal in the vast majority of countries. It is usually against the terms of service of most social networks though but social networks have a whole bunch of things to do at any givent time so I would imagine you have a pretty high chance of getting away with it.
Since you are able and allowed by FB to change the name, contact details, email and everything connected to this account I don't see why it would be illegal.
On Twitter, it is also illegal but there are many people who do this but it is not good and by doing this you just break the trust of your followers.