Do I still have to pay my half of the mortgage if I move out and my girlfriend doesn't?

It is never wise to purchase real estate while still unmarried.
Lenders rarely drop a borrower from the obligation to pay the loan. Also by being a joint borrower legally means you have joint and several liability with the gf (that is you are both liable for the entire loan),.
Assuming your name is also on the deed, you can sue for partition which means the house is sole and you both take 1/2 of the equity left after the mortgage is paid.
You might find my legal guide on selecting and hiring a lawyer helpful.
You might find my legal guide on Is it Legal? Is it Illegal? helpful.
You might find my legal guide on the understanding the different court systems helpful.
You might find my legal guide on legal terms used in litigation helpful.
(Even if you are not filing a lawsuit this information can be useful).

You might find my legal guide on commercial litigation helpful.
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You might find Gabriel Cheong’s legal guide on the do and don’t of finances after a divorce helpful.
You might find my legal guide on divorce in general and in NJ helpful.
(Much of this information is valid for unmarrieds who have children together).

The prior federal administration severely weakened most state’s laws against excessive interest. Unpaid debts now have practically no ceiling on interest which means the final bill can be much more than the original debt.
When you have received a collection notice, lawsuit or even a judgment on an old debt which may have already been paid, or belongs to someone else, or has been discharged in bankruptcy, keep the following in mind. After a creditor writes off your debt, it can then be sold to a collection agency. That agency may sell it again and the next one again. By the time the debt is assigned to a law firm, it can be years pass the statute of limitations, all of the original contracts have been lost and there may be no legal foundation for enforcing the debt. One way of knowing this is that the agency will have no discernible address or they will say they are collecting from a creditor, but the creditor does not know who they are. They will call you at work , and they will not listen to any explanation at all. They will refuse any suggested payment plan and demand a large sum at once. Often these collection agencies and even law firms will file a suit against you, misspell your name, or deliberately send it to the wrong address. You have no notice but they go to court anyway, get a default judgment against you when you do not come to court, and file a judgment lien on your assets such as a home you are trying to sell, or they report you to a credit bureau as a deadbeat. You are allowed to send a 100 word explanation in writing to the three credit bureaus (which they must print) as to why the debt is invalid. Also, many attorneys will take such a case on a contingency basis. A Violations of the fair debt collection act has a fee shifting rule (the creditor pays your attorney). Not only do you get the debt out of your life, you may get a financial award also. Be sure to write to your congress representative to have a stronger federal law to restore a ceiling on interest and to curtail these illegal collection practices.


LEGAL DISCLAIMER
Mr. Sarno is licensed to practice law in NJ and NY. His response here is not legal advice and does not create an attorney/ client relationship. The response is in the form of legal education and is intended to provide general information about the matter in question. Many times the questioner may leave out details which would make the reply unsuitable. Mr. Sarno strongly advises the questioner to confer with an attorney in their own state to acquire more