This is a nice debate topic, because we'll have a clear cut answer next year. If you truly believe there is at least a 50% chance of Democrats controlling the house or 20% chance in the senate, you can make some easy money:

house: https://www.predictit.org/Market/2704/Which-party-will-contr...

senate: https://www.predictit.org/Market/2703/Which-party-will-contr...