@David126, forgot to add the following, this is from the official Airbnb online help center. This also confirms what they told me on the phone, and it is clear from this that it is up to us to determine if age restrictions are allowed in our state. When it is one's personal residence, federal law does allow us to have age restrictions. Here is the excerpt from the Airbnb website:
"Is placing restrictions based on a guest's age or familial status prohibited by law?
Because housing laws are complex and are applied differently in many cases, Airbnb can’t provide personalized guidance on what restrictions to age or familial status are permissible for your listing.
The U.S. Fair Housing Act (FHA), for example, protects families with children from discrimination in housing where the listing is offered as a "dwelling." Longer term listings of several weeks may qualify as a dwelling, depending on the particular circumstances.
California's Unruh Civil Rights Act, meanwhile, prohibits "business establishments" from discriminating in the sale of rental housing on the basis of age. Both laws contain exceptions for certain types of accommodations, such as housing developments for senior citizens.
We encourage you to be candid in your listing about what features you believe may be unsafe or unsuitable for guests of a certain age or families with children or infants, and to discuss any concerns with potential guests. You should also learn more about the housing laws applicable in your area, and consult an attorney for advice."