I don't think is a good idea start a site with only NHL & NFL games, but are better start with completed sport, because people like me, see the site for the first time, not see football match to bet and exit and don't back

If your idea is a site like directbet (when you bet without account, only send btc to address and later received) you have more work, because directbet is more trusted and send a win immediatly later a game (and if you win when the game play, example bet over 1,5 and later 10 minutes score 2 gol, pay later few second)