how to persuade my brother to get us a brushcutter?

We really need one as I cannot get to the tap to water for bindweed and
nettles and the paths are horrible uneven between the beds.
I've offered to pay half and he says "just beat them down with a fork"
My problem is that I've been diagnosed with osteoporosis, and broke my ankle
from merely crouching to load my woodburner. So I don't want to chance
uneven in case I do it again.