Ketu's mahadasha which lasts for 7 years in the native's life brings about detachment form material world. Ketu originally represents detachment, spirituality, enlightenment, letting go of things we desire, interest in occult knowledge, isolation, psychic, and asharams. During the mahadasha of Ketu one experiences sudden fall from their relationships, material wealth, loss of status and reputation, unless the depositor aspects or sits with Ketu. Most people have always experienced some sort of hardship regarding the house where Ketu was placed in. They suddenly feel no interest towards the things where Ketu resides. They want to get to the truth of life and existence. This is why many seek astrological knowledge, occult knowledge and tarot knowledge during Ketu's mahasasha or antra dasha because of the occult aspect. If Ketu is forming a Raj yoga by being placed in Kendra or trikona then there could be great gains in such times. Ketu doesn't always gives all the things we talked about but that's what it represents. People usually take foreign journeys to holy palaces have sudden interest in monks and monetary or isolated places event through they might be getting gains in such time period.
If the native's Ketu is in the 7th house then there could be sudden separation, detachment or lack of interest in marriage, partnership, business or career in general since 7th house is 10th from the 10th. Ketu in 5th house can suddenly show separation from children having lack of interest in raising children and creative purists. If Ketu is in the 6th, 8th or 12th house then sign placement and it's depositor's position is very critical because that will determine if the native will have good experience through such houses, usually malefic planets do well in dushtana houses, however, there are sensitive placements that can go either way. If the depositor is in kendra and strong by sign placement then Ketu dasha will bring victory over the things related to such negative houses, if Upachaya house then it will improve over time, especially if Ketu dasha comes in 40's it will give far better results due to depositor being in a upachya house. Ketu is that one planet that is most sensitive to its depositor's placement. Usually all planets can handle themselves even if the house foundation is weak, but Ketu who already wants to let go of material things, wealth and relationships needs a tight grip on his leash to keep our material world under control because we living in a 3 dimensional plain where we have to pay bills, raise kids, go to work and find shelter. Ketu is blind to such things and doesn't care except to find the truth about the source energy.