Divorce from wife

Sir, This question pertains to my friend Kumar. He has been married for 20 years and has no children. The marriage life was no good and still he adjusted. 7 years ago his wife brought a child to his house which she claims to be given by her brother. Kumar said he cannot accept the child since it was not a legal adoption. she forged fake documents in name of the child like birth certificate and aadhar card etc. Later she even managed to get an adoption deed registered in name of child where a fake seller was brought in. for 7 years kumar has approached many authorities for justice. His wife threatened him if he does not accept the child she will accuse him of domestic violence and so. So he left his house and lived far away for years. Last year the child was acquired by child welfare committee on his complaint. Now the lady who had left kumars house a year ago wants to return to his house to disturb his peace and wants money. Kumar wants divorce. Kumar does not have any regular income since he is retired but has many properties in his name. If he files for divorce what will he have to give his wife. Also note that the marriage was not registered in register office and hence no marriage certificate. Kindly give me details on divorce proceedings.