My hosting expired yesterday and I may not be able to renew it for several days.

How long until the website appears offline?

It's a wordpress website on bravenet... I don't know if that makes a difference.
If I go to the website address now, it's still there even though it expired yesterday?

If hosting has expired you get a page that says Expired so that would mean to renew hosting.

It is a weekend so bravenet will be in office tomorrow so I wouldn't hold off too long on your hosting.

Just make sure your Domain doesn't need renewing as well.