6th lord in 1st House or ascendant 
You may also read First house lord in 8th house. It is not considered good as 6th house gives obstacles so native may face a lot of obstacles in life path. 1st house is personality house so ill placement in 1st house may give weak physique, weak health, diseases etc. Bad placement of the planets may give long term disease depending upon the lord of the house and zodiac itself. 

However, well placed 1st house and 1st house planet in own sign, excellent sign, mooltrikona sign, own house, friends’ sign will reduce the evil effect and native will enjoy good and sound health and strong physique. 6th house belongs to legal matter so native may suffer from legal issues. If this placement is good then it may give career in in law fields. 6th house makes the person argumentive, and well placed 6th lord make the person very good in arguments.

6th lord in 2nd house: 
6th lord in 2nd house, if not well placed, is not good placement in terms of wealth, family relationship etc. Native’s relationship with family members may not be on friendly terms, there could be legal (6th house) battle, dispute, misunderstanding, or even fighting within family. 

It is possible that native may lose wealth due to enemy, disease, legal problems given from 6th house. He might have taken loan or borrowed money from others which he may not be able to repay and suffer harassment or penalties. If well placed then native may earn through legal profession such as judge, lawyer, or court staff etc.

6th lord in 3rd house 
This placement could give enmity (6th house) with siblings, neighbours, or colleagues (3rd house). The bad relationship with siblings may land in some dispute or legal trouble. It is also possible that native does not have any siblings as per the 6th lord. 

6th house belongs to maternal uncle (mama), its lord placed in 3rd could mean that uncle is playing the role of baddie among siblings and creating troubles. However, good 6th lord will provide good life to siblings. 6th house promotes argument and 3rd house being communication house increases this pattern, native will be very argumentive in nature in most of the cases. 6th house is opposition, and 3rd house is initiative, self-effort etc., native will have to face opposition/competition in his initiatives, however, he may overcome this if 6th lord is good.

6th lord in 4th house 
It also works as first house lord in 11th house. 4th house is upachay house (11th) for 6th house so 6th lord in 4th house may gain strength. However, generally speaking 6th lord placed in any house in chart will create trouble in native’s life.

6th house lord may create obstacles in the 4th house significance of study and education in native’s life. 6th house enmity brings loss in happiness in the 4th house takes away peace of mind of the native. There may be fear in his mind (4th) due to enemy (6th). This placement gives a flow of negative thoughts to native which creates restless mind.

6th lord in 5th house: 
It is also not considered good as 5th house belongs to your past deeds and it is occupied by L-6, it is possible that native is suffering in his current life due to his past deeds.5th house is prominent children house, occupied by L-6 which may cause disease or illness to children and even in some cases – death as 5th house is markesh (2nd from 5th) for 6th house. 5th house is intelligence; L-6 will take over this intelligence and replace it with the 6th house attributes of quarrel, argument etc. Native will easily get into arguments, fight over small issues and not use his brain to settle the things.

6th lord in 6th house: 
It is a good placement if 6th lord in 6th house is in good shape it will help to increase the significances of the 6th house. It said in astrology that lords of inauspicious houses are better placed in its own houses. 

The powerful Trik (3rd, 6th and 8th) lords in their own houses provide power and competitiveness to the native. However, native may be affected with health problems, long term incurable diseases. This placement ensures close affinity with the maternal uncles of the extended family, and native may receive great benefits from them. It is possible that native does not have good relationship with other relatives.

6th lord in 7th house: 
It may also read as 1st house lord in 2nd house. 6th lord in the seventh house creates difficulties in the marital relationship may end up in divorce. It is possible that native partner is of calculative nature, over passionate, aggressive and always in dispute with native. Either native or his wife character may be suspected. Remember 6th house also gives debt and litigation, so partner may be the source of debt and legal problems. Partner may be interested in high living standards causing financial instability to native due to the sixth ruler being the twelfth from the seventh.

6th lord in 8th house: 
6th is obstacles and 8th is also obstacles to it is like minus multiplied by minus equals to plus. Since 8th house belongs to hidden or secret things, if 6th lord sitting in 8th house is in good position, the person could work in secret organizations, in medical field (6th house), he may earn money from litigation, lawsuits (6th) or inheritance (8th). 

However, this placement also gives serious health problems, long term debts, legal problems, and hidden enemies. Such person will not be faithful in relationship. He will have strong drive towards sex, and may be indulge in immoral sexual activities.

6th lord in 9th house: 
It can be seen as unstable fortune for the native. 9th house is father house; it may cause health problems for native father. Native may not have good relationship with father. Well placed 6th lord in 9th house may reduce this effect. His father would belong to judicial system (6th house belongs to litigation), or he may have some illegal source of income.

6th in 10th House: 
6th and 10th both are artha(money ) houses, so if placement is good, it could prove beneficial to the native as a Lord of upachay house placed in another upachay house depending on position and conditions of 6th Lord in 10th house. 

However, as a natural malicious place, 6th lord will create obstacles in native’s professional life. He may not get top position but he will be in better position serving others. He may have frequent changes in his career. He may have enmity (6th house) at workplace (10th house). In case planets are weak, native may experience job loss or loss of reputation due to some reasons.

6th lord in 11th House: 
This is an interesting placement as 6th lord is placed in the 6th house from 6th house. So in some cases it might be beneficial to the native. 11th is your friends’ house, it may give enemies among friends so one has to be careful with his friend circle, may give birth to jealousy among friends. Same goes with elder siblings. 

Such placement may give benefits through dealing with servant, labour, or lower class (6th house). This benefit may not be in a moral or righteous way.

6th lord in 12th House 
It is also interesting placement of 6th lord in 12th house – the house of dissolution as both the houses are dushsthan and houses of losses, so loss in the loss also becomes profit sometimes. Which means if planets are in good condition the native will overcome the problems related to enemies (6th), debts (6th), and diseases (6th) easily which will dissolve in the 12th house so this placement provides notably beneficial effects to the native. These benefits will be more visible during the dasha of the 6 lord.