My neighbor borrowed my trailer and had an accident. Am I involved?
Potentially yes, as the owner. Liability while towing generally attaches to the towing vehicle’s policy, and you can still be named, particularly if the trailer was poorly maintained. Two policies may be in play and most people assume only one is.
Should I stop lending things?
No, and it is worth knowing the exposure exists. Keeping equipment maintained, showing people how to use it, and carrying sensible liability limits covers the realistic cases. It is a reason for an umbrella rather than a reason to be unneighborly.
What if they pay me a little for it?
That starts to look like hiring equipment out, which is a business pursuit and excluded from personal policies. Informal payment is enough to raise the question. If it happens regularly, tell us, because it needs a different arrangement.