I’ve been to many houses and I’ve seen my bit of mould and other, in most cases it is caused by the way household habitants are actually living in them.
Mould is man made
With this in mind one should make himself familiar with few conditions that mould needs to grow and spread it’s toxins( which as a matter of fact can be harmful to humans). For mould to grow in a first place room has to be cold, moistures and without great deal of air flow.
Few ways that people create those conditions in their rooms:
Draying clothing without opening windows
Not having ventilation in the bathroom
Not ventilating the room
Not having heating on often enough
Now if you understand what mould need to grow in your home you can prevent those conditions to be in place, once you achieve dry, and ventilated rooms mould will hate you. Now, if you have some mould you just need to treat it with some good antibacterial chemicals and wash it well. If you’re happy with result and you’ve resolved environmental causes you can paint it off and it should be gone for a long time. I would recommend as a first course of action to asses your home and check if there I’d no outside moisture source.