Building materials will always wear off as the years go by. Roofs would leak, paints would peel, cement will crumble, foundations will weaken. Which is why it is important to have a sort of "maintenance fund" if you want to build a house or a building. More so if you buy an old house or a building. This is because when repairs need to be done, it will definitely cost something. And you wouldn't want to repair only when something bad already happens, right?
Just like most people, I would want to save on the maintenance works as much as I can and would opt to make it a DIY project. But when doing major repairs or renovations, it would be smarter to have professionals do it since it would be more efficient that way. No back jobs so to speak. To my friends in Canada, let the pros do the foundation repair in Ottawa or anywhere else. I would also recommend to do waterproofing ottawa works on the roof and walls so that your homes are safe from mold growths especially in the cold winter time. The minor repair works like changing hinges or repainting, that you could DIY.
So there... Happy saving! :)