An Idaho Limited Partnership costs $100 to file with the Idaho Secretary of State.  You file a certificate of limited partnership.

The required info is:
• The name of the Idaho limited partnership  (Must contain LP or Limited Partnership in the name.)
• The mailing address of the principal office of the Idaho LP.
• The name and physical address of the Idaho registered agent.
• The name and mailing address of all the general partners.
• If the Idaho LP is limited in liability.
• The signatures of all general partners.

The formation of an Idaho LLC, can often be simpler to run and maintain than a Idaho LP. 
Either way, you will need an Idaho registered agent and the Idaho LP forms are in your online account immediately after you sign up for service.