Jupiter is the planet of prosperity and well-being. Twelfth House is the house of losses. Twelfth House belongs to Saturn and is associated with Prison and other forms of Bondage. Jupiter from a materialistic perspective is not that good in Twelfth House. However on a spiritual plane it can provide Moksha which is liberation from cycle of life and death. Only other planet capable of such feat in Twelfth House is Ketu.

     Jupiter signifies abundance and Twelfth House signifies sleep. So its natural that native loves to sleep a lot. Not only that native may have good imagination unless bad planets are associated with Jupiter. Jupiter gives chance to travel and settle in foreign countries. Jupiter being the planet of well-being and prosperity can make for a favorable experience living in foreign countries. Jupiter promotes good relationships with father's siblings as well the children of those siblings. If Jupiter is associated with bad planets then there could be lengthy prison sentence, house arrests or something similar or even depression. If Jupiter is associated with Saturn then one should expect some sort of prison sentence or restricted movements once in their life atleast. 

     Jupiter's aspect on Fourth House gives a favorable home environment and a caring mother. It also gives a big house and chance to invest in real-estate, live stock and farming. Also native can possess good vehicles especially luxury cars or high-end bikes. Jupiter's aspect on Sixth House is not so favorable for health and promotes obesity. It gives good employees and a good job. Environment at job place is friendly and caring of the native. Jupiter's aspect on Eight House should provide chance to invest in mutual funds and government bonds. Also native maybe able to get good inheritance. 

     According to B. V. Raman those with Jupiter in Twelfth House could make fun of others beliefs and lead a lustful life. Later on they do repent and reform. Natives are anxious about their ornaments, vehicles and clothes. 

     Jupiter in Twelfth House is definitely bad from materialisitc perspective. On a spiritual plane it could lead to connection with higher self or even God in some instance. Those with Jupiter in Twelfth House should try to stay away from illegal activities, drugs and alcohol. It could lead to prison sentences. They need to pray to Lord Shiva in addition to Lord Vishnu. Prayers to Lord Shiva are better when dealing with heavy portfolios of Twelfth House. Also native should exercise regularly and keep weight in check. 

References:
Raman, Bangalore Venkata. How to Judge a Horoscope. Delhi: Motilal Banarsidass, 2014. Print.