What's In It For Me?
Why might a rural property-owner want to take in homeless workers on his or her land? Right off the top of my head, I'd say, "For the labor they must contribute to earn their keep, which will multiply the productivity of the land."
A lot of factors have to be in proportion to make the Common Wealth Farm concept work.
#1) Your property must be near an underserved market for produce of about 50,000 people.
#2) You must choose those you allow to live and work on the land carefully.
#3) You must carefully balance the desired quantity of production - the ammount of fruit, vegetables, eggs, whatever - that you are confident you can sell with the number of workers and the space available to feed them and grow the saleable produce.
#4) The workers you accept must feel they are getting a good deal in return for their labor, so they are motivated. (More on this later.)
In a real estate market that is experiencing deflation of value, while being whipsawed with a crosscurrent of potential oil-based input price escalation, putting people to work growing vegetables organically appears to be the safest, least-risky option for the property owner to get a return from their land. Remember, your labor to produce these goods is virtually free.
I haven't yet worked out a strict business plan for the Common Wealth Farm concept, but from my "horseback estimate" of its feasibility, it looks good.
There may be tax advantages to taking action privately to help the city/county/state with its growing homeless problem, but I will not factor this in yet.
On the other hand, using farmland to grow nursery stock would appear to be a losing proposition for the next few years, as a major slowdown in homebuilding is worked off.
Growing large acreage crops, using tractors and combines requiring fossil fuels and multiple spray applications, then selling the crops at a small margin of profit likewise doesn't seem to be promising for the next few years, unless you are fully confident that some type of affordable alternative fuels and fertilizer/pesticide input can be found quickly.
My personal inclination is toward producing food crops with only human and animal labor and organic methods, then selling direct to a relatively small audience of CSA customers at competitive prices. This gives the farmer a free workout and keeps input costs down, while providing a high-quality local product for an appreciative audience. Win-Win-Win!