For low-income housing funded through HUD, the answer depends on if your boyfriend/girlfriend is eligible for the program.
The boyfriend/girlfriend must provide a social security card and birth certificate or acceptable form of citizenship identification. Also income documentation will be required and the new addition to the family must pass a criminal history background check. The process will take some time, usually no more than thirty days, but do not move anyone in until you get the appropriate authorization. If you do move someone in before you get permission, the person will be considered an unauthorized household member and you can be terminated from your low-income housing program. Private pay renters should check the lease and get permission from the landlord or apartment manager. If children are coming along, they must provide birth certificates or an acceptable form of citizenship identification and social security cards as well. The unit also must be big enough to accommodate the new members of the family without overcrowding.