What are my rights as half owner of the house?

You may have little opportunity to make this work out well.  Remember the old adage, "neither a borrower nor a lender be."  The point of that is to avoid just this problem.  If you forgive me for adding, "no good deed goes unpunished."  Now you are a part owner of the house and stuck.  I assume that the original owner was/is a friend and that by itself has some value to you.  I also assume that the original owner does not have enough money available to pay off the money you  "invested." Your choices:  1) talk to your "friend" about him or her getting a loan from a bank to pay you back/buy your interest out.  If they can't do that consider 2) talking to them about selling the house, either to you or to some third party.  If it is sold to a third party, perhaps all the debts are paid and you can each get back to relative normal.  If it is sole to you, they will have some money to move elsewhere or you could rent it to them.  If they won't go along with either of those, you could 3) file a partition action in court, essentially getting the court to sell the house and divide the proceeds.  This could be pricey and you will end up losing the friend.  The court may also find that you aren't entitled to 50% because the judge may thing that you took advantage of the dire straights of your friend.  Even before you consider the legal fees that you will both have to pay (which may eat up all of the proceeds from the sale and more), you are not likely to get your entire investment back, unless this is a really desirable property, in a good market and there is a small or no mortgage on the property.  Your last choice is 4) count it as a lesson learned and don't do it again.  Of course, that depends on how much you invested and how much you are likely to get back on any of the other solutions.