For a closet-sized area, the quoted range is within the expected spectrum. The significant price difference usually reflects the scope of inspection. The lower quote likely covers cleaning the visible growth, while the higher one probably includes diagnostic tools like moisture meters and borescope cameras to check inside the wall cavity. This diagnostic step is critical; without identifying and stopping the moisture source, the mold will return.

Attempting a DIY fix with vinegar is not recommended for porous materials like drywall and shoes. Vinegar may temporarily clean the surface but will not address the root moisture problem or penetrate deeply. A dehumidifier is a good long-term preventative tool but is not a remediation solution for an active infestation.

Given the musty smell and the building’s age, the mold has likely spread behind the drywall. Disturbing it yourself risks releasing a large number of spores into your living space. The most prudent approach is to have a professional assessment to determine the moisture source and full extent. They can then provide a detailed scope of work, which allows for more accurate and comparable quotes. You can then decide if the remediation is within your DIY capabilities, though for occupant safety and property protection, professional remediation is strongly advised for suspected concealed growth.