My 2 sister in-laws have 2 kids sleep on the same bed till they are around 8. One of them is one boy and one girl.
Of course u can try to post to sell 2nd hand, no guarantee u will get a good price. U can donate to poor people. Every bed has gap and mold on the wall next to it. If it is 2-level, it is too heavy to move to clean the mold.