1917 Cartoon - We've seen this kind of economy before

I can't imagine land prices in Vancouver are any higher than they were in London during the war. 

I know nothing about the real estate market of London of that era.  I am looking for someone to give me the rational business case for farming on $150/sf land because I cannot honestly think of one.  A gravel parking lot would earn better economic returns than farming (unless they farmed pot).

That assumes that the price of food stays cheap and the demand for parking continues to stay high.  The reason the Victory Gardens started in the UK was because of rationing and food shortages. 

Yes.  Rationing interferes with natural market mechanisms and drives prices higher so I guess at some point there would be a case.  I think, however, that mass starvation by those who could not afford to pay such high prices would come much sooner.

The cause for food shortages was the war and not some kind of regulation (rationing and otherwise).  When only a small portion of the population can afford food it is not bad social policy to preserve a share of the food supply for people unable to afford it.  Otherwise there would no doubt be widespread rioting and looting. 

History aside, my point is that in an environment where food is scarce you may find yourself growing food.  Nothing could be closer to the free market than that. 

I am not against the idea but it seems to me that farming in non-rural settings is only something that the wealthy could afford to do as it would be a luxury.  First you have to have land.  That means you either rent or own the land.  Either way using it to farm would be a choice only someone who already has enough land on which to live could do.  Otherwise they would only be able to afford enough land for their housing needs.  Keep in mind I am assuming ann urban setting like Vancouver where there is no real "surplus" land.

Using my house as an example anyone who has a spare $600,000.00 laying around or the credit to borrow that sum would simply be better off using the land for a higher use and taking the proceeds (rent) and simply buying food produced on more suiitable, less valuable land.  It is a situation of comparative advantage.

This logic makes sense in a textbook but realistically people aren't going to rent out their backyard.  The reality is that this isn't a futuristic scenario.  In fact the cool kids in Brooklyn are already doing it. 

And then there is this house in California.

I reviewed your examples and they reinforce my point.  These people do not suffer from food insecurity due to economic conditions.  They are making lifestyle choices not economic ones.  You original point was that economics could force people to do this and again I maintain that will never happpen as the underlying economics do not make any sense.  As a lifestyle choice I agree that some people make choices that are not strictly "profit maximizing" but when one takes the concept of "utility" into account many wrong economic choices make more sense.  We all do this but the motive for it is not an economic one as you suggested originally.  Hell I grow some of my own food and it would be much cheaper for me to buy what I grow from Safeway when you take all costs into account but I derrive utility from the process.