Your sister can live separately from him and once they are living separately than there is no issue of his liability to take on her shoulder or son shoulder.

File for divorce by mutual consent 

2) consent terms should mention that wife would be absolute owner of x properties and husband would relinquish his share in those properties and vice versa 

1.  See your sister is not.liable for her husband's Liabilities see though on his death if she inherit any of his properties she is liable for that if any debt is there.

2. See in this case it is better to take mutual.divorce and settle properties.  

Ans:- As far as legal separation goes, there may occur such circumstances that your sister may have to be liable for the liabilities undertaken by her husband. 

For safeguarding the properties, please let me know if there exists any properties in their joint names. If only they have properties in joint names then only those properties can be safeguarded. 

1.  The extra marital relationship is no more a crime, hence he cannot be punished under criminal laws for this.

However she can file a divorce case on that grounds alone by proving his adulterous life.

The proeprty lying on each other's name shall be their own property and each other have no rights on the properties owned by other's properties at least not during their lifetime.

2. Your sister cannot be held liable for your brother in law's liabilities or debts until she had signed as a guarantor or surety to any debt or loan availed by him.

3. They can decide about getting their marriage dissolved by filing a mutual consent divorce instead of continuing this dead marriage.

- As per Supreme court  , Adultery is not a criminal offence, but is a ground for divorce.

1. As per law, you sister is not having any right over the properties of her husband during his life time, but she can claim maintenance amount and residential right from him. 

2. Similarly , your sister is not responsible for any liabilities of her husband . specially if no property transferred by her husband in her name. 

3. If, her husband dont wanted to live with her , then your sister can take mutual divorce from him on her conditions.

Good luck and dont forget to rating Positively.

You need to contest the case if filed by any party. 

She will not be liable you can also give public notice

That's their personal discretion about separation or no separation

1. They should take mutual consent divorce from each other.

2. Your sister will not be liable for giving the loan taken by your jijaji. 

3. Mutual separation will not be enough in this case they should get divorce from eachother.

1. Your sister is not liable for the debts of her husband unless she is a guarantor to any contract between her husband and the lender.

2. The only legal separation is in the form of dissolution of marriage for which a mutual consent divorce petition can be filed in the competent court. Even without divorce then can live separate but the legal relationship will continue to subsist between them,

1. Spouses have no right of share in the property of another and hence there is no question of taking any safeguard.

2. The liabilities of your brother in law is not going to make your sister liable in any way.

3. If they are not dissolving the marriage then there is no need to ponder over these issues any way. 

4. Your sister though if has no source of income is entitled to maintenance from her husband @ 1/4th of his income. 

Your sister is not bound to pay the debts of your bro in laws in fact they cant do it legally or morally.

it is better file for mutual consent divorce.