Arbitrage betting certainly works.
An 'arb' is when a bettor places multiple bets on the same event to guarantee a profit no matter the result. The process usually involves hedging using two or more betting accounts simultaneously.
Sports arbitrage is profitable due to discrepancies between the odds at different betting sites. You can learn more about how arbitrage betting works from my article: Does Arbitrage Betting Work?
Yes, sports arbitrage is perfectly legal.
It's simply a case of placing bets at the available odds using multiple betting accounts.
Arbitrage Betting is however discouraged by Bookmakers and doing so usually breaks their terms & conditions — but this in itself isn’t illegal.
You’ll need specialist software to identify arbitrage opportunities.
There are some free arbitrage bet finders available online - but they have several limitations.
If you want to find the best opportunities before they disappear, and maximise your profit from arbitrage betting, it’s essential that you upgrade to a paid arbing service or ‘arb finder’. The best ones are listed in my review: Best Sports Arbing Software
Eventually, yes. Arbing is profitable and, unfortunately, the bookmakers are under no obligation to allow winners to continue betting with them.
Once a bookmaker detects that you're placing arbitrage bets, they'll restrict your stakes or even close your account entirely.
There are however ways that you can prolong the life of your betting accounts. Check out: Prevent Your Bookmaker Accounts From Being Restricted.
Arbitrage betting is difficult to sustain because profits are reliant on bookmakers accepting your stakes.
Once a betting account is limited or closed, you won't be able to continue using it for arbitrage. So in that sense it's a short-term money maker.
However, some arbers are able to get around this problem by using a Bet Brokerage Service. Others opt to graduate onto other forms of professional betting, such as: