Or in other words be very wary of and don’t accept free things. Let alone “free” services!

Better upfront cost than hidden backdoor cost.

For example house sitting for a friend — keeping it clean, hidden things that break, garden infestations that have to be dealt with, etc. And cleaning it again once you leave.

Even getting a free car — having to keep it clean, maintain it, change the oil, shovel out the snow and get rid of ice in winter, etc.