A good customer texts you. They tip every week, and they want to know if you can do them a favor. The favor is extra work, and the way it's asked makes it sound like the tips already paid for it. You like this customer. You don't want to sound ungrateful. You also don't want to start doing free work. What do you say?
A tip is thanks for the job you just finished. It isn't a deposit toward the next one. Once you see it that way, the answer gets easier. You're not turning down a favor. You're treating the extra work the same way you'd treat it for anyone.
Say yes to the favor, kindly and with a price, and you keep the good customer and your margin.
You don't have to choose between caving and getting prickly. Thank them, say you'd be glad to do it, and give them the price. Something like: "Thanks so much, we really appreciate you. Happy to take care of that. It would be [price], and I can do it on your next visit." It's warm, it's clear, and it keeps the door open.
This works because it's consistent. The extra work gets a price whether the customer tips or not. Once a customer hears it from you once, they know how it works, and nobody feels awkward the next time they ask.
In Run My Lawn Biz, quote the extra as its own line so the customer sees exactly what it costs. Then add a property note about what the regular visit includes, so next time the line between the visit and the extra is already clear.
Thank people for their tips, price the extras kindly, and you keep good customers without giving your work away.



