Do you know anything about FHA loans/HUD?

My sister bought a home on an FHA loan 27yrs ago. We moved her into assisted living a few months ago, because she has some health problems and cannot live on her own. She has 3yrs left to pay on her house, but since she is getting government assistance with her assisted living, she has to give up her house. She can't pay the monthly payments. The house is going to go into foreclosure unless she sells it. I have offered to buy it, but they are requesting I take over the HUD loan. I would just like to pay cash and get it out of her name. Whats the best way to go about it? They say I have to pay a huge amount of some type of assistance. They say she has $70K worth of back payments I would have to pay. Whats the gig? Do I have to pay all that, because I really can't afford that? She needs some upgrades on the house like siding, windows, some weak spots in the floor fixed, and a bathroom remodel.

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