I agree that these aren't really "problems"; rather, they're things you're looking to handle in a more convenient way.
Mail: It's not hard to use bill pay to schedule "future payments". Even if you don't have the bill yet, just estimate how much it'll likely be and pay that amount. If you pad it just a bit, you'll just owe less the following month.
It's really easy to go online and stop your mail while you're gone. You can choose either to have it ALL delivered on a certain date after your return, or you can tell them that you'll come to pick it up yourself. I agree that probably 90% of my mail goes straight into the trash can.
Clients calling you: Do you have any partners or competitors who'd appreciate picking up this work while you're traveling? Sure, it might not be a great financial choice, but maybe you could work out an agreement with them so they'd give you similar situations while they're out of town -- and hopefully it'd equal out.
Rental property: Since you weren't physically there to do the work, I think your wife calling a repairman was the best option. You can't always optimize everything, and keeping a loyal renter is more important than a one-time bill.
Garden: Yeah, it's easy to hire a teenager to follow your instructions, but I understand where you're coming from -- if you'd been home, you'd have noticed the change in weather and would've adjusted your watering appropriately, but you can't leave ALL possible alterations for a caretaker. And, ultimately -- unless your neighbor is a fellow gardner AND has unlimited time to help you out, caretakers don't care as much as you do. Perhaps you could avoid scheduling lengthy trips during the summer, when your garden's in full swing? I've heard of putting your plants into a kiddie pool and covering them with plastic to "hold in" water, but that won't work for more than a week and wouldn't work with anything larger than house plants.
Similar "problems" that bother me a bit -- obviously, not your problems since your wife and son were home:
- Coming home & the house is hot/cold & the water heater is turned off.
- The refrigerator is empty of fresh food.
- Unpacking and washing clothes.
- Picking up the dog from the kennel; he gets soooo worked up.