The scariest con of a Cohabitation Agreement...
When a couple gets married, certain rights immediately accrue to the other. This includes being the person a healthcare worker may consult to make life saving or compassionate decisions of the affected partner.
In the case of the death of one of the partners, the surviving spouse of a marriage would automatically inherit from the deceased’s estate if that person died without a will. The same does not apply to couples in a cohabitation relationship. In addition, no term in the Cohabitation Agreement that aims to provide for the other on their death will be valid. In other words, if your partner died without nominating you as a beneficiary in a valid written Will, their estate would be distributed to their descendents, or to other members along the family bloodline - including those very, very distant members if they are the closest surviving family members of the deceased.
Although a Living Will, Durable Power of Attorney, and a Last Will and Testament can go a long way to resolve these issues, they may be changed unilaterally by the person signing them at any time. They are therefore useful tools to regulate a cohabitation relationship, but certainly not fool proof in protecting the interests of both partners.
Any of this scare the pants off you?