Buying Parent’s home for what they still owe, is it allowed?

[William Richard Arens]

My Father started a company a few years ago and is currently at risk of losing his 2 million dollar lifesavings if he cannot sell the company (intellectual property holding company). Instead of losing his home, he would rather sell his home to me and then I would rent it back to him. Is it allowable for me to buy his home for what he owes? The home is worth between 600-700k but needs work. He still owes about 350k and wants to sell it to me for that price. They currently pay 4k per month on their mortgage. I want to buy so i can take out a HELOC and finance other investments. They want to sell and rent from me to lower their payment and offload the asset in case of future bankruptcy. Is this legal? Would I be able to get a mortgage on this type of deal? Thank you all!