Look up all the legal sportsbooks in your state/country that offer welcome bonuses. Hedge these welcome offers against each other. I made over 50k from those alone.
For example:
BetMGM is offering a 100% first deposit bonus of $1,000.
Caesar's Sportsbook is offering a 100% first deposit bonus of $1,000 as well.
The Dallas Mavericks are playing the Minnesota Timberwolves.
The odds are 1.55 for the Timberwolves to win and 2.50 for the Mavericks to win.
You deposit $1,000 into both sportsbooks. You now have $2,000 in both accounts.
Now you place a $2,000 bet on both sides of the game.
On BetMGM you place $2,000 on Dallas: $2,000 pays $5,000 ($3,000 profit).
On Caesar's you place $2,000 on Minnesota: $2,000 pays $3,100 ($1,100 profit).
No matter which team wins, you will end up with a minimum of $1,100 profit since you only deposited $2,000 across the two sportsbooks, but of course you want Dallas to win for the maximum profit
I did this for every legal sportsbook in my state and made over $50,000. It's not a matter of "if" you will make money, it's a matter of "how much" you will make depending on how many underdogs win. As a successful football (soccer) handicapper myself, I was able to maximize my profit and made over $50,000.