Vent: My mom's "helpful" loan offer had a catch I didn't see coming

For years I thought any family money talk was about being ungrateful if you said no. Then last month my mom offered to cover my $4,000 car repair, but she wanted me to sign a paper saying I'd pay her back with interest at 8%. I almost agreed on the spot because it felt rude to question it. Then my cousin pulled me aside and showed me how her "no interest" loan from our aunt turned into a 6-year guilt leash. That convinced me to ask for a written agreement with a clear end date, and my mom got all huffy about trust. Now I'm wondering if setting limits with family is really about protecting them from their own bad habits, not just yourself. Has anyone else had a relative offer money that came with hidden strings they only spotted later?