So when you see a book offer a Risk-Free Bet Up toR$1,000  it simply means that if you lose you'll get the amount of your initial wager back in something other than cash, and if you win, the book has decided that you don't really deserve anything extra.

This is called your betting unit size. We typically recommend that a sports investor bet 1%-3% of their bankroll on each bet. Conservative sports investors (or beginners) should bet 1%-2% on a play. Note that professional's betting unit sizes are normally in the 1% range.