The length of time to sell a business depends on several factors. The asking price is a key factor in that if a business is priced at a premium, above market value, it will take much longer to sell as it will receive far few inquiries than businesses that are competitively priced.
The industry is also a factor in the time required to sell a business. Manufacturing, distribution, and B2B services tend to have more inquiries than retail.
Another factor is earnings, businesses earning over $250,000 are in more demand than businesses earning less than $100,000 and tend have more inquiries and sell faster (assuming they are priced competitively).