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There is considerable evidence that smoking cannabis can provide effective pain relief for many conditions which commonly affect pensioners, and growing your own has the benefits of convenience, assured quality, reliability of supply and cost savings.
If you have a spare bedroom, it can easily be converted into a high yield cannabis factory, and within a few months, you should be harvesting sufficient quantities for both your own needs and your immediate circle of friends. Excess production can then be sold to augment your pension.
If raided by the police, you should stress your age and infirmities as immediate defences, and if the case proceeds to court, make sure you arrive in a wheelchair with an oxygen cylinder attached and collapse onto the floor clutching your heart as soon as the prosecuting counsel asks their first question.