Fair housing

      
          Federal fair  housing laws make it illegal for landlords to deny tenant applications based on race, gender, ethnic origin or background, religion, family status (having or not having children), or disability  (mental or physical). Also some state laws prohibit discrimination based on age, marital status, or sexual orientation.
Some examples of illegal discrimination may  include, advertising based on group characteristics mentioned above, not making  selecting criteria equal for applicants, refusing to meet the needs of disabled tenants, ending tenancy for a discriminating reason. 
        Landlord can select tenants based on credit history, rental history, minimum income requirements as long as these standards are the same for all applicants.
        A tenant or applicant who thinks landlord broke the fair housing laws should
contact a local HUD (dept. of housing and urban development) office or visit the website www.hud.gov. If there is a reasonable basis to believe that fair housing laws have been broken, HUD will find a mediator to negotiate with landlord to settle the matter. If settlement is broken later too, HUD will likely recommend the Attorney General file a lawsuit. If the alleged discrimination is violation of  a  state law,  tenant  can file a complaint with state agency responsible or such claims.
Also sue the landlord in (federal or state) court.