Question for unmarried couples living together

Hi, how do you protect yourself sa ganitong set up? I mean I know na mas okay na separate ang savings, investments, and properties should be named sayo kung ikaw lang ang bumili nagbayad. Pero I was thinking if one of you buys a house and then the other person ay mag aambag sa renovations etc how does that work pag naghiwalay? May habol ba yung nag ambag since wala naman pangalan niya sa title ng bahay?