When Jill Langen decided to list her Clarkston, Michigan, home of 25 years for sale last month, she did it without the help of a real estate agent. Seven days later, she had an agreement signed with a buyer and her home was off the market. Langen’s decision to go it alone isn’t typical among America’s home sellers. Just 6% of home sales last year were for-sale-by-owner (FSBO), an all-time low, according to an annual report by the National Association of Realtors, the trade organization that represents over 1.5 million real estate professionals. However, some homebuyers and sellers may be...