Not got full access to our website - admin worries

We chose an individual not a company to develop our new wordpress ecommerce website which is about to go live. We are delighted with all the work that has been done and the functionality of it.

We understand now that we will not be given full access to the all the admin but we can of course edit all the content and e commerce settings. It seems this is the industry norm and it never occurred to us at contract stage to ask about copyright etc. and who owns what.

Our only concern is that if something were to happen to the developer, where do we stand? We have no passwords to access all the back end of the site. If the developer were to stop working for any reason and payments to their server were to stop, our site would not exist. We have been advised that site back up should be made and given to us. But not being technical we don't know what this back up should include or consist of or what the technical name for it is, so can't ask the developer. Can anyone advise us as to what we need to ask for to give us some security.

Any advice will be much appreciated.