Hi, I'm looking for a wordpress plug-in in order to book and pay rooms of a bed and breakfast. Do you have any cheap or free suggestions?

Here are some good offerings, they seem to be free.

However to integrate payments seems like you will need some customization work.

https://wordpress.org/plugins/wp-simple-booking-calendar/

https://wordpress.org/plugins/wp-booking-system/

https://wordpress.org/plugins/booking/

I think you might end up paying more for a free one. WooCommerce has a booking plugin that although not cheap, is one of the better options for WordPress booking systems. http://www.woothemes.com/products/woocommerce-bookings/ It's not cheap but you could probably set it up on your own if you know your way around WordPress. This could also take care of some of the issues with payment gateways and multiple currencies although further plugins may be necessary depending on what you are doing.

 

Otherwise here is a list