Assuming the mortgage of my parents house?

[Carl Trube]

Howdy y'all! 

My mom would like me to assume the loan of her house to ensure it remains in my name. She and my stepdad would continue to live in the house and pay for everything (e.g., utilities, mortgage, etc.). Essentially I would become the landlord and they will be tenents. House is currently valued at about 400K. It was purchased for 193K. The remaining FHA loan is 120K. All of us have stable jobs and no other outstanding concerns. The family dynamic isn't a major concern.

Does it seem pragmatic? I'm vacillating because I don't want to miss out on any legal, tax, and other considerations (i.e., Does their equity transfer to me?). 

Maybe y'all can provide your insights.