Can I draft a binding contract?

Ok my girlfriend and I want to purchase a home together. Hoping to catch a good deal on a fixer upper in a nice neighborhood. For reasons, I don't want to be listed on the mortgage. But I have the monies for down payment , closing , renovations etc. Now is there anyway this can be reflected in a legal doent outside the mortgage? Just in case the relationship dissolves my involvement in house is recognized. hopefully it will not come to that but, expect the worst hope for the best. Thank you for your comments and suggestions