You’ll pay roughly $40-$100 for a template specifically designed for guest houses or bed and breakfasts. They usually look great but the performance is not always the best.
The main issue is that they usually use unique ways of configuring so if you want to change in the future, then you’ll need to go through the setup again. They also only last as long as the theme creator decides to keep it alive. Older themes are also less likely to not be coded to current standards.
Divi is a paid WordPress Theme.
You can use one of the popular free WordPress themes and use a supported starter site/starter template on top of it to make it work for your establishment. Of course there are far fewer options than the paid versions.
Some themes have a free base version with add-on or premium features you’ll have to pay for.