How to get a family member renting a room from on a rental assistance program

[Peter Korty]

Hello smarter and more experienced real estate investors!

I have a question for you all that have some experience with tenants on rental assistance programs. 

My sister is renting a room to her father-in-law and her husband is in the process of divorcing her. Her rental agreement with her father-in-law is $300/month with a hand shake. Her lawyer told her that she really needs to increase the rent she is charging her father-in-law to to $800/month, but when we were looking at her finances today, she has only actually been getting $150/month. She doesn't want him to leave because he helps to take care of everything that his son never would, like picking the kids up from school, fixing things around the house, mowing the yard, and taking out the trash. He also doesn't want to leave living with my sister and her kids either, but really can't afford to pay more than the $150/month that he's barely able to pay now.

Both my sister and her father-in-law are very low income earners, and the house they live in is too much for her to pay for on her own. Her soon to be ex husband was the only reason they could afford the house in the first place and he isn't paying for anything anymore, so I'm trying to help her figure out a way to keep paying her mortgage, or at least reduce her payment to an amount she can afford.

Do any of you know of a way to get him on some kind of rental assistance program in the Indianapolis Indiana area? Ideally she'd be able to get the full $800/month that she could use to help reduce her mortgage payment.

Thanks you very much for your help, it's much appreciated!

Pete