Although rodents and insects like to hide from sight, they do tend to leave evidence of themselves behind. One of the telltale signs of rodent and insect activity in a rental unit is the presence of their excrement. And gross as it may seem to study pest droppings, learning to recognize them will save you from renting a place where you'll have to deal with the pests on a daily basis.
Mice and rats leave as many as 50 fecal pellets a day, so chances are you'll spot some if you have an infestation. Mouse droppings are about the size of rice grains, while rat droppings are as big as raisins. When fresh, the rodent droppings are dark, moist, soft and shiny. Old droppings will be a dull gray.
Roach droppings will look different, however, and actually resemble black pepper pellets. Also, watch for roach egg cases, which can be brown, dark red or black, and appear smooth and shiny. Bed bugs leave behind dark brown or black excrement that appear as small spots, usually on mattresses or around tiny holes that serve as hiding spots (such as gaps in a bed frame).