It's not betting. You choose a team of players from the teams and gather points based on their actual performance. It will be impossible to choose your entire team from the Eagles as there will be a draft.
Keeper league is where you get to choose one player from your previous season's team to keep on your team this season. You forfeit the 1st rd draft pick in most league configurations. The NFL is such a transient league that it really doesn't make sense IMO to retain a player bc so much can change from coaching scheme, to the team around the player that affects their performance.