purchase home from mother

my mother-in-law married 5 years ago. after the marriage she bought a condo which she and her husband now live in. they have a pre-nup but we are not sure of how accurate or specific it is. her husband has a signficant amount of debt, some from before the marriage, some from after. my mother-in-law will eventually need to sell the condo to be someplace cheaper and more accessible. her husband is older than her, and we are concerned that if he dies before her, creditors could come after the equity she has in the home when she has to sell it.

we are considering asking her to transfer the deed of the condo to us (her three kids and their spouses) in order to protect the equity. she still owes on the condo (worth 200k+, owes about 100k). we would take out a mortage to cover what is owed and ask them to pay rent to cover the mortgage. we're concerned for their wellbeing, and committed to doing what we need to, to take care of her and her husband but unfortunately we can't take on a second mortgage without the rent to help cover it.

i'm wondering about what options we have for structuring the transfer, and what potential tax consequences for my mother-in-law and for us might be. any advice, suggestions or warnings?

thanks in advance.