It is possible according to this case in Delhi: Woman to pay alimony to sick husband

Now in above case the application for alimony was made by wife and not husband. However based on merits of case the court decided that it was the ill husband who was without any means to support himself or take care of his illness, and so he was granted Rs 500 / month as alimony from wife.

Is it legal? Yes it is! The Hindu Marriage Act (HMA) 1956 clause 24 says this for maintenace during divorce proceedings:

24. Maintenance pendente lite and expenses of proceedings.-

Where in any proceeding under this Act it appears to the Court that either the wife or the husband, as the case may be, has no independent income sufficient for her or his support and the necessary expenses of the proceeding, it may, on the application of the wife or the husband, order the respondent to pay the petitioner the expenses of the proceeding such sum as, having regard to the petitioner's own income and the income of the respondent, it may seem to the Court to be reasonable.

It is as clear as can be that the intent of the law is to enable the party without means to be able to do his/her pleadings in the case.

Now read clause HMA 1956 clause 25 which relates to permanent alimony/maintenance after divorce.

25. Permanent alimony and maintenance.-(1) Any court exercising jurisdiction under this Act may, at the time of passing any decree or at any time subsequent thereto, on application made to it for the purposes by either the wife or the husband, as the case may be, order that the respondent shall pay to the applicant for her or his maintenance and support such gross sum or such monthly or periodical sum for a term not exceeding the life of the applicant as, having regard to the respondent's own income and other property of the applicant, the conduct of the parties and other circumstances of the case, it may seem to the Court to be just, and any such payment may be secured, if necessary, by a charge on the immoveable property of the respondent.

Again it is clear that Hindu marriage laws relating to alimony also supports either party to receive alimony and maintenance.