Mercury in 8th house. 

So, lets see what Mercury can do in 8th house without any conjunction or aspect from any other planet. 1st lets see what these 2 things represent --

Mercury represents communication skills, marketing, calculative ability, younger siblings, hobbies, skills with hands, intelligence, quick decision making, logical thinking, youthfulness etc.

8th house is house of secrecy, occult knowledge, death, transformation, death and re-birth, In laws family, joint wealth with spouse etc.

So, this can be termed as the most powerful placement for becoming an Astrologer. As it is house off occult and hidden science and Mercury is significator of Astrology, this placement may make an excellent Astrologer. These people would also love to communicate about occult and hidden science to people. So, a blogger/teacher on occult can be seen with this. 

As 8th house is house of in-laws family and Mercury represents communication, this person is highly communicative with in-laws. 8th house is also a house of taxes and Mercury represents calculating skills, so it is a good placement for becoming an auditor too. 8th house is also other people needs and Mercury is a counselor, so it shows a career in counselling people in their needs. It is also a house of death and rebirth, Mercury is a businessman, it shows someone in business of life insurance or someone who deals with inheritance or bankruptcy matter. 

From 8th house, Mercury aspects the 2nd house of Family, Speech etc. whereas Mercury itself is Communication, it shows that this person has good communicative relation with his family. 

Hope this helps. Thanks,

Swami Premanand Bharti