As mentioned, you DO have mold in your house but if you keep living conditions in check it cannot generally complete the growth recipe and become productive.
If you have a mold growth issue in your home then you also have (or have had) a moisture intrusion issue in your indoor environment. There are many potential sources for high moisture indoors. Some of them are leaky plumbing, caulk & grout failure, plumbing overflows, sewer backups, leaking roofs, building siding, windows, foundations, damp crawl spaces, inadequate ventilation, improper insulation, sources of humidity from cooking, laundry, aquariums and humidifiers and other sources. Home building occupants experience some sort of moisture intrusion as a result of one or more of the foregoing conditions, but the key is monitoring, being diligent in prevention and quick, thorough response when something happens. These simple and generally inexpensive upkeep and maintenance will keep expensive repairs and remediation efforts from being necessary.