I read this in George Orwell's "Down and Out in Paris and London".

Orwell was down and out in London, going from spike to spike. (Spikes were homeless shelters. You would pay for a bed or in some cases just a cell. You would have to be there for a mammoth long time, doing absolutely nothing.) Orwell calculated that each day England's population of homeless people spent ten years staring at walls.

The two main problems with homeless people were: they were idle, they were hungry.

The solution is obvious: make them grow their own food. Turn all the spikes across the country into vegetable gardens with accommodation. You don't have to pay to get a bed (or cell); you have to do a bit of gardening. Then you can have some nutritious veggies and some sleep.

Solving those problems solves yet another problem: their general health, which was appalling, as they had no fruit or veggies in their diet.