I am not actually sure if freebitco supports the change of account email address, but just check it yourself.
It does.
If you go to your profile, you will see a option to change your email address.

The problem is that even if the new owner changes the password, the old owner may be still able to regain access to the account.
TheQuin's post:
Whilst there is no rule against buying or selling accounts it is very risky for the buyer. It would be very easy for the seller to claim the account was hacked and prove original ownership to get the account back.