(as) poor as a church mouse

Very poor; having little or no money. My father was as poor as a church mouse growing up, so his sole focus was to give his kids every opportunity in life that he missed out on. We've become poor as church mice ever since the bank raised the interest rates on our mortgage.

very poor. (*Also: as ~.) My aunt is as poor as a church mouse. The Browns are poor as church mice.

Having little or no wealth and few possessions, as in She's poor as a churchmouse, so you can't expect her to donate anything. The reason for this long-used simile is unclear, but most believe that, since churches are not known for storing food, a mouse inside one would fare poorly. It has survived such earlier phrases as poor as Job. [Second half of 1600s]

If someone is as poor as a church mouse, they have very little money. I was as poor as a church mouse, but I bought that wreck of a car. I suspect we'll continue to be poor as church mice. Note: Mice living in a church are unlikely to find much to eat as there is no kitchen or food cupboard.

Singularly impecunious. This simile dates from the seventeenth century and its original analogy has been lost. Most authorities speculate that since a church usually has no place for food storage, such as a mouse might invade, mice would fare very poorly in churches. Indeed, James Howell’s 1659 proverb collection states it as hungry as a churchmouse. The current cliché has outlived the even older and once more common poor as Job (who in the Bible was deprived of all his possessions by Satan), poor as Lazarus, and poor as Job’s turkey (which, according to one of Thomas Haliburton’s Sam Slick tales, had only a single feather).