Fair Housing Act is a federal act in the US intended to protect the buyer or even renters from discrimination. It makes it unlawful to refuse to sell, rent or negotiate with any person because of that person's inclusion in a protected act.
This means that even if you're not a real estate agent you cannot discriminate based on someone's race, color, religion, sex, national origin, familial status or physical or mental disability. This is protected under federal law but state and local protections can also include a variety of extended classes including LGBT, citizenship, someone's age, veteran status, genetic information, sexual orientation, gender identity, income or political ideology.
Discrimination means that you treat someone differently based on their inclusion in a protected class. You can't deny renting to or selling to someone because they are a single woman, a person of a particular nationality or income other than if they cannot afford it based on term requirements.
Related: How Hard is it to Buy a House if You're Single?
Even suggestions could be perceived as discriminatory regardless of whether they are well intended or not. Real estate agents cannot make certain statements such as, "this would be a great house for a young couple," a person with children or even ask simple questions on whether or not they are married. This can cause a legal headache. However, landlords are able to ask who will be on the application and the rental agreement but may not ask their status. If you're going to ask one renter a question you'll need to ask it as a general rule but again, not discriminate against a particular protected class. You cannot rent a one person because they are white and then deny someone else because they are African-American if they both can afford the property and pass necessary checks.
Disabilities are also an interesting protected class.
In 2014 alone over half of the housing discrimination complaint have something to do with a disability. These are extra protections that landlords need to be aware of to accommodate renters. Disabilities can include a wide range of mental or physical disabilities but landlords and sellers cannot ask whether a person has a disability which could include people with visual, hearing and mobility impairments, mental issues, HIV, AIDS or even a history of disability. You can only ask questions that could be asked of every applicant or tenant. It simply not a good idea to walk the line on this and to avoid any questions that would cause a renter to question your intent on particular questions.
Families is another protected class. There are certain stipulations that can limit children in particular situations such as communities that require only 55 and older residents. Sellers, real estate agents and landlords cannot specifically state that an area is "kid friendly" or recommend someplace that's close to a school however, they can state that the property is within a certain distance from the nearest school and talk about general school ratings. This is not stating whether or not the property would be appropriate for children but if families with children are looking, this might be something of interest.
Advertising a particular property can be discriminatory if it appears to favor or even exclude particular groups. Real estate agents often have a hard time avoiding "steering" certain people to a particular area. They need to stay as unbiased as possible and as general as they can. However, there are certain guidelines that are in place to the general well-being of most people. This includes "maximum Occupancy Guidelines". Certain codes require no more than two people per bedroom. The Building Officials and Code Administrators state that there must be 150 ft.² for the first occupant to 100 ft.² for each additional resident. "Every room occupied for sleeping purposes by one occupant must contain at least 70 ft.² of floor space, or at least 50 ft.² per person occupied by more than one person." [Source]
It's a slippery slope but if agents, sellers and landlords do their homework and really try their best not to get into any awkward situations, most of the time everything's fine, but you just never know. How can homeowners avoid this? Using a great property manager or agent to do the job for them. Homeowners don't have to do the research on what to do and what not to do and their agent can handle it all.