The difficulty of adding a basement to an existing house can vary depending on the house’s location, the size of the basement, and the type and condition of the existing foundation. Adding a basement is a job best handled by the pros, so you’ll need to enlist professional help for this project.

The time it takes to finish or remodel a basement can vary significantly, ranging from a few weeks to several months or even up to a year. On average, the construction phase can take four to eight weeks, but the total project time can extend to three or four months when including planning and permits. The timeline depends on several factors, including the basement's size, design complexity, the scope of the work, and your contractor's availability. A more detailed breakdown for an average-sized basement might include: framing (3-5 days), electrical and rough-in plumbing (3-5 days), drywall installation (5 days), flooring (2-3 days), and final touches like painting and trim (about a week). If preliminary work like installing a waterproofing system or addressing structural issues is needed, the timeline could extend to six to twelve months. Factors like difficult access, material transport, and ventilation needs can also add to the project's duration.

Whether it’s more affordable to gut a house than build a new one depends on the markets where you'd be buying and selling. However, it’s usually less expensive to renovate a home than to build new construction. 

Most homeowners pay between $100,000 and $200,000 for demolition and remodeling costs, whereas the average cost to build a new home is between $139,000 and $531,300.

Although it’s not required, air ventilation in a finished basement can help improve the air quality, prevent moisture and mold issues, keep musty odors away, and also maintain the air quality throughout the rest of your home. Proper ventilation will help maintain the value of your investment in finishing your basement. Try basement ventilation methods like installing vents or a dehumidifier for best results.