It's possible for a couple to live together without anything financially binding them together; however, if they choose to live together with financial dependency there can be legal issues involving debts, bankruptcy, and more.
It's also important to note that if your spouse is financially dependent on you they might be able to work towards getting off of your tax return (if this applies) or get their own; however, if they are disabled keep in mind that you will still need to claim them as a dependent on your tax return.
When it comes to debt and bankruptcy, you should also know that this can affect both spouses and the decisions made will depend upon where they live. For example, if one spouse files for bankruptcy protection, the other might be required to file too – depending on where they live. If they don't, it could make things worse.
If you believe that your spouse is depending on your income to survive, you might want to check with a local bankruptcy attorney or one who specializes in family law for advice. It's important to have legal guidance when decisions are made so both spouses can be prepared for any future problems.