Rendering is the step where your storyboard becomes video. Up to that point nothing has been generated and nothing has been charged.
Build the storyboard first: pick the property, pick the photos, set the order, and choose your format. When the storyboard is how you want it, start the render.
Each scene is animated into a clip, then the clips are assembled with your opening and closing cards into the finished tour. You can leave the page. The work continues on Avenue's side and the tour appears in Completed when it is done.
You need at least a few photos for a tour to be worth making, and more photos means a longer tour. Choose the ones that show the property well rather than every photo you have; a short strong tour beats a long thorough one.
Credits are charged per animated clip, and the cost is shown before you confirm.