An informal "keep an eye out" understanding with a neighbor works better when it's specific rather than vague — for both of you.
What to agree on explicitly
- What signals to watch for (mail piling up, blinds not opening, lights on during the day)
- What to do if they notice something — call you first, then a designated contact
- Whether they hold a spare key, and under what conditions they'd use it
Making it reciprocal
Offer to do the same for them, or offer something else of value (mail pickup during their travel, plant watering) — mutual arrangements tend to be more sustainable than one-directional favors.
A short, written note (even a text message confirming the agreement) prevents the "I thought you meant something different" problem later.