If you discover mold during your search and it’s a small enough problem (meaning it’s in a small patch on a hard, nonporous surfaces like metal or glass), it can be tackled while spring cleaning. Make sure to put on protective gear like gloves and a face mask, though. Direct exposure to this indoor contaminant as well as to the particles kicked up into the air during remediation can trigger adverse health reactions.
Simply spray a disinfectant cleaner (I personally recommend Benefect Decon 30) on a microfiber towel and wipe away the mold. For the toilet specifically, turn the water off, flush the toilet a few times, and use a spray bottle to coat the entire interior (including the lid) with the cleaning product. Allow this to sit for a few minutes before wiping it away with the microfiber towel.
For semi-porous surfaces like grout, use 8% hydrogen peroxide and a microfiber towel. (Again, be sure to wear gear for this!) Spray the hydrogen peroxide on all of the grout in the tub or shower, and let it sit for at least 10 minutes. Then, wipe with a microfiber towel.
If the mold comes right back, it could indicate a larger issue that requires a professional. Hiring a mold inspector to come in can help determine if there’s a hidden problem elsewhere.