Smelling mildew under your mobile home?

this could be an animal that tried to crawl under and died.

Ans 2 - OR, and much more serious, could be from pinholes in old copper pipe or cracks in old PolyB pipe (which was very popular in '70-'90.) wetting the bottom of floor !- Damp or even rotting particle floorboard is VERY common in mobiles over 25 years old ! Check carefully by walking and putting your foot down heavily all over floors especially between kitchen and bathroom. If it feels springy or soft then it must be replaced. NOT always a huge job. You can replace it in sections usually.