The fact of the matter is, the whole Do-It-Yourself approach is really more valuable before the infestation, by taking measures to prevent a mice infestation in the first place. Once your property is already invaded by the pests, you really need to know how bad the problem actually is. Because you can get the mice you see walking about, but you can rest assured there are a lot more where they came from. And that's what need to be done - you need to find their nesting grounds and face the problem head on. This is a tough job to on your own :/ If your concern about pest controllers is the use of pesticides, you should know that there are many options. Most qualified professionals start with traps and most importantly - sealing the cracks and crevices which the mice use to sneak into your house. When they find the nest, that's when they apply poison and yes, it can get quite unpleasant then. Dead mice could be an issue but you can request the exterminators to come for a second visit and access the situation (and possibly clean up the mess) Good luck to anyone who had the misfortune to deal with these rodents!