into mowing lawns, would be to spray the weeds at each job, and
include it in the original price you quote.
I came from a retail background and thought "add on sales" means more
money. But I ended up with some clients who wanted weeds sprayed, some
who didn't, some who complained if it cost more, some who would never
get them sprayed until their were too many to kill in one go.
I would have to leave jobs unsatisfied with how it looked, but being
proud of your work is half the pleasure of working with your hands.
So I eventually realized it wasn't worth the hassle trying to add on
sell the weed spraying. I would do a quote, say $55 to Mow Snip Blow
and Weed Spray every 3 weeks, and that's what was included. If some
weeks only needed a tiny bit of roundup (non name brand of course)
then so be it, if they needed more, no worries.
After a while, my job got easier as it wasn't too hard to keep the
weeds at bay, rather than deal with an overgrown jungle. The client
was happy because the price was the same each week. And I could be a
little happier knowing I was improving the place each visit.
Of course, I hate poisons and if someone gives you a natural feasible
alternative go for it.