It is dangerous to work for someone who thinks they are doing you a favor by employing you.
Because if they think they are doing you a favor, they won’t think that your work is valuable.
And they won’t treat you like someone who is doing valuable work.
And, often, this means they don’t feel obligated to pay you, or don’t feel obligated to pay you on time.
It also means that they’re likely to think that you owe them something aside from the work you’re paying them for. For instance, they might think you owe them free tech support, or to pick up their dry cleaning, or any number of other time-consuming inappropriate favors.
It’s not always avoidable – if you’re in a difficult place, you might not be in a position to avoid working for people like this. But when you can avoid it, it makes life a lot better - and even when you can’t, understanding what’s going on helps.