Bovada LV has set the Cleveland Cavaliers as 15/4 odds to win the NBA Finals in 2018.
This means if a person bets four dollars on the Cavs and Cleveland wins the NBA Finals the person gets 15 dollars in return. The Golden State Warriors are the favorites to win the NBA Finals at 4/7 odds.
The Brooklyn Nets, Orlando Magic, Phoenix Suns and Sacramento Kings have the worst odds to win the NBA Finals at 500/1. You can see a full list of odds at this link.