Triangle corner garden, preferably raised beds if possible

Elderly neighbour unable to maintain his garden through health issues. At present he pays for his front lawn & hedges to be maintained. Rear garden has become a small wilderness. I suggested that maybe he could let someone use his rear garden as an allotment but instead of monetary payment possibly look after the front lawn & hedge in return. Not sure if thats allowed or possible but if you dont ask you can never get. Really gets the sun early morning to mid/late afternoon if that makes a difference. No tools provided water can be supplied.