Verizon Communications is considering entering the multibillion-dollar market for sports betting, which could become legal in the United States before the year is out, according to people familiar with the matter.The New York-based phone giant, which last year bought Yahoo and its popular sports fantasy business, has been meeting with consultants to assess the potential for a sports-focused online gambling venture if the laws in this country change, said the people, who asked not to be identified discussing private information.