Royalties on Patents and Audit Rights

Many inventors come up with a great idea and wish to sell this idea to another company in trade for royalties for use of their patent. This makes sense because the inventor does not have to start his own company and go thru all the risks to build the device and can sit back in his home workshop and come up with his next invention or innovation. Often these inventors when making an agreement do not put in the contract that they want audit rights to the company