Set Aside In Rental Or Sales
I know there are various set-aside or preferences like 55+, affordable, etc. which are all legal.
Is saying these units are set-aside for someone working or stationed at Los Alamitos Army Air field.?
I believe that you can do so.
Your list of "preferences" actually has members of two different classes of tenants and a full fledged answer would require a somewhat longer answer.
The most basic rule is that you may choose or refuse to enter into a lease (contract) with any person for any reason EXCEPT the prohibited ones. The prohibited reasons for refusing to rent or sell are race, color, religion, sex, handicap, familial status, or national origin. In addition in-so-far as renting is the extension of credit you cannot discriminate because the source of income is some public assistance program.
Some cities or states may have laws which protect other classes of tenants so you must check on this as well.
The 55+ communities are an exception to the "familial status" law which exists to protect retirement communities from being invaded by families with children. So while in general you cannot discriminate against tenants who have kids if you ONLY rent to persons over 55 you have an exemption from this rule. As a person over 55 with children under the age of 5 I find this a little strange but then I have no desire to move into a retirement community with the 2 year old.
Now there is an interesting outgrowth of this rule which is that you may not refuse to rent for any reason which is a "surrogate" for one of the prohibited reasons. If, for example, the employees of the Air Field were predominately white and the non-base employees in the area were predominately black then a prosecutor could argue that your preference for Air Field employees was a proxy for racial discrimination which is prohibited.
Turning to "affordable" as a category it represents a different situation. I am unaware of any jurisdiction which has an "affordability" definition which would prohibit you from reducing or modifying your rent so that it is affordable.
Rather this is not a legal prohibition but a contractual obligation. Various programs exist to subsidize housing costs so as to make the housing "affordable". If you take the money you enter into a contract to rent in accordance with the guidelines of the program and the definition of maximum household income is likely to be requirement of your contract. If you break this provision of the contract they can sue you in civil court but you are unlikely to see federal criminal violations.
So, unless the local discrimination police can argue that your Los Alamitos preference is actually a disguised discrimination against one of those preferred categories the answer is yes-- you can have a preference for such tenants.
At least as far as I can see-- perhaps others with wider vision will see some other problem.
Turning to "affordable" as a category it represents a different situation. I am unaware of any jurisdiction which has an "affordability" definition which would prohibit you from reducing or modifying your rent so that it is affordable.
Leave it to CA.
If a property is set-aside as below market rate (sale or rent), That property can not be rent to someone that makes more that the BMR criteria.
So is I said Military only, rather than BMR only, that sounds o.k, since the set-aside is defined up front and likely a covenant on the deed.