Purchasing real estate is just that:  a business transaction.  Despite popular belief, marriage actually affords individuals a legal benefit to share in the assets acquired during the course of the marriage and in some states, it also includes those items acquired prior to the marriage and brought into the marriage and maintained by both parties during the course of the marriage in some form or fashion.  Therefore if you "must" purchase real estate with a joint owner who is not your spouse, then you "must" follow these rules:
 
1. Ensure that both of your names appear on the title of the property at some point only after the following nine (9) points have been completed as written below.  If you fail to complete 2-10, you cannot do #1.
 
2.  Determine the legal manner in which title will be taken (i.e., joint tenancy or tenants-in-common) if both of your names will appear on title.  For example, if upon your death you want your share of the property to pass to your children or your heirs instead of to the joint owner of the property, you would hold the property as "tenants-in-common". If you want your share to go "only" to the joint owner, then "joint tenancy" would be your best choice. (Check with your local real estate attorney regarding your state's applicable laws)
 
3.  Talk to a real estate attorney (not a criminal/civil/accident/etc. attorney) to sort out the options available in your state and decide what should occur with each of your respective shares if you were to become disabled, terminally ill or pass away. 
 
4.  Find out if either party is currently married or is currently going through a divorce.  (You might find yourself in a legal battle with your significant other's spouse who he/she failed to discuss with you.)
 
5.  Make sure you are aware of all of the children of your joint owner/significant other  (the real estate might become subject to litigation in a child support proceeding)
 
6.  Have your joint owner provide a current copy of his/her credit report. (Note: all judgments and tax liens will attach to the real estate when real property is transferred via a Quit Claim Deed.  Therefore if your joint owner has a judgment for an outstanding child support matter or any other matter, that lien will automatically attach to the real estate that you now own together). 
 
7.  Develop a plan for the real estate in case either of you elect to not remain in the relationship/partnership/friendship.
 
8.  Have a minimum of six (6) months of full mortgage payments saved (not just your share) in case of an emergency/break-up/argument or other unfortunate event.
 
9.  Determine the roles that you will have with respect to the real estate.  Who will maintain the property, who will pay the bills associated with the property?
 
10.  Write out your answers to questions 2-9 and then answer question #1.  ONLY when all answers to questions 1-10 are in writing, should you consider purchasing property with a friend/family member/significant other that you are not legally married to.

God Bless,
Attorney Deadra Woods Stokes