Shops are listed in the facilities section of the rules, but they are not listed as income-generating and they don´t appear in the faction-specific list or in the "available to all" list. So what are they good for and who can build them?
Shops are NPC-only facilities. If you want to have something similar, you can ask a Trading faction to build you a Commerce Centre. I think it also contains a shop NPC that is able to sell basic items, if not you will probably be able to place on there in the future.