Old can be a huge problem in a home, and the problem is that once you have it its very difficult to get rid of. Controlling the moisture in your home should make it easy to control mould, so make sure that you clean and repair any damage to roofs and gutters as and when you notice them.
When spills occur, clear them up as quickly as you can, as stagnant water can cause mould. If you see condensation accumulating on the windows make sure that you dry it off and clean it as soon as possible as mould is known to spread quickly.
If you do not have a fan in your bathroom, make sure that you ventilate well after anyone has showered by turning on an extractor fan and leaving the door open. This will make the room dry out quickly and minimise the event of moisture accumulating.
If you notice that mould is growing beneath the floor then the room is far too damp and this could be toxic. Spray any contaminated area with bleach and water spray, making sure that you have the correct clothing on and have your nose and mouth covered. Leave it to soak in for a few minutes and then wipe clean. Make sure you identify the cause of the wetness and remedy. You may need to install a dehumidifier.
Make sure that you have Home Insurance to protect your house and its contents; cheap policies are readily available online for your convenience.