Dear babbler,
Joomla is a content management system with powerful functionalities. Create Username and Passwords for the persons whom you want to give admin rights like making changes in the content of your site, that is to manage your site along with you. Then mail the username and password to those people. After loggin into your administrator account of your Joomla site you can do that. Users can be allotted different rights like Super Administrator, Administrator etc. as you wish. Control the users from your administrator panel. You don't need to give the details of your hosting account or password to others. Never do that. It is dangerous. Your hosting Account and your Joomla administration is two different things. Don't confuse them please.

mukundguruji