I think growing food will entail building the biggest infrastructure in space, and may even determine what social structure will develop. Anyways, to make all this worthwhile, ie profitable, plants should do more than just provide food, oxygen, and clean water. A lot of other things could be provided by plants such as organic compounds. Not all things are made of aluminum and titanium after all.

Plants can supply resins and fibres for composite materials, glue, seals, gaskets, air filters, noise proofing. Other possibilities are tough airtight fabrics for spacecraft or remote-controlled rovers' wheels. These same fabrics can be used for inflatable structures as a primary shell before a permanent layer of cement is sprayed around the interior. These large structures could in turn be used to grow more plants, to build more structures, and so on. There is bootstrapping potential here.

Of course the difficulty in all this is that capitalism relies on the proximity of a market. At present the only market for products is the population here on earth. As such there may not be very many ways of getting a growing facility going in space, or on the moon. One possibility is bootstrapping, where the intention is to increase the value of the product in situ in order to attract customers to it, rather than attempting to bring it to market. One example of increasing the inherent worth of a potential product is refining minerals such as aluminum or titanium. A million tonnes of cold rolled metal alloy just sitting there on the moon could be very tempting to investors. Such refined materials could be useful for countless applications, such as larger structures to house paying tourists, rocket fuel storage tanks, and more of the same stuff you've already heard elsewhere.

On a slightly different note, does anyone know of any advantages or disadvantages of placing a station at the L4 Earth-Moon Lagrange point versus putting it at the L5 point?