I find used kiddie trailers all the time, usually without the stroller attachment, but some with it. Varying condition from pristine to downright ragged.

Keep your eyes open, and you may snag the trailer of your dreams for $100 to $150... give or take a little.

I'm not sure I'd be comfortable taking a ragged looking trailer into a store, but some could be cleaned up quite nice.

I did make a mistake on one and try to take off the upper section, and realized that a bit of fabric left on the trailer is actually good for protecting wheels, giving the load some support, and helping hold the load in place without lots of straps.

I've heard of trailers being stolen, but don't know the circumstances. So far, nobody has messed with any of my trailers, whether parked outside of a store full or empty. So, I never think about trying to take it into the store.

I have filled up empty reusable shopping bags while wandering around a store, then dumped them out at the checkout line (good way to verify capacity). But, I don't think I'd feel comfortable putting unpaid for items into a half full personal "cart".