Retaining original owner on deed on a sub to deal

[Russell Smith]

Hey friends! 

I am attempting to structure a deal where I am added to a deed as a 50% owner. I would assume all aspects of management including finding renters, maintence, paying the mortgage, etc. The original owner of the home would retain his 50% equity and be completely hands off. We would keep his mortgage. 

If the owner is still present on the deed (though my name would be added) would their be a concern for the due on sale clause to be called? Also, when adding my name to the title, is there a way to stipulate equity ownership? Thank you thank you for any insight from those who have experience w/ sub to!