Rents may be caused by tangible assets (e.g. oil and gas) and by intangible assets (e.g. patents).
Some pharmaceutical production plants do not own patents. In that case they may sign a license agreement with the owner of pharmaceutical patents. This is an example why it is important to distinguish the producer and the asset owner. It is the asset owner who receives rents, in this case the owner of the patents.
Rents 