I imagine this could be very awkward.
A trip to the cinema, for example - who would pay for your wife? After all your wife may not want to see the film, and if the other person paid it would get very expensive.
More worryingly, could your wife be deemed negligent if someone in her care had a fall or other incident?
As the minimum wage is around �5 an hour I think an elderly person who needs assistance would rather pay from practical help such as cooking and cleaning.
It would need a lot of research first, but basically a good idea.