Yesterday my neighbour washed my car for me... it was in the path of her watering the herb garden I've set up on the footpath as she pointed the hose over her front fence, so she thought she'd keep going once my car got a bit wet. While I was away other neighbours all chipped in and kept an eye on the garden, passing the responsibility to water it each other if they went on short holidays, perhaps taking a few leaves as they did. Neighbours and passers-by have commented on what a lovely idea the garden is. Someone left an empty pot next to it on the footpath to add to it. (Someone else took the time to amuse themselves - and me - by rearranging every single label into a different pot!) It's getting noticed, no-one has treated it badly, it's started conversations with strangers and it's now almost covering up the graffiti that I planted it for in the first place, a few more pots and some vigorous growth once the weather cools down a bit should do it.
I've used recycled pots and mainly cuttings that I've propagated myself (although I couldn't resist adding a chilli plant that I'd bought) so the only expense has been some potting mix and wire to tie the pots onto the pole supports. That way, if it didn't work, it would be no big deal. Being vertical it takes up minimal space and doesn't intrude into the footpath walking space. I try to keep flowers going in it to give some colour and make sure that everything is edible and labelled so people will know what they are trying if they want to take some leaves.
Do you have a power pole outside your house? Maybe you could start a neighbourhood herb garden around it?