Almost anybody can start taking advantage of sports arbitrage, but to make a worthwhile income, I suggest that you'll need the following:
Permission to gamble
It must be legal for you to gamble. If you're under 18 or live somewhere where gambling is illegal then sports arbitrage is not for you. If you live in the USA then it is likely that you are not permitted to gamble. Bookmakers require you to specify your country when you join their websites, so you may be blocked from gambling if it is illegal in your country.
A reasonable amount of money to invest (your "bank")
OK you could start using sports arbitrage with only a few pounds (or similar in your own currency). However you must remember that your profit will be a small percentage (typically 1-5%) of your total investment in each opportunity. So if you only invest £10 in a 5% (which is a good return!) arb, you'll only make 50p profit! Therefore you need to invest as much money as you can in order to show good returns. I would suggest a started bank of a couple of thousand pounds in pretty much essential. A bank of £500 might show returns of £20 per arb, which is not bad at all if you're doing this part time to generate a little bit of extra cash.
It's not wise to invest money that you need to pay the bills because events can be delayed and bets settled late. Only use money that you afford to leave invested for a while.
Plenty of free time
You're going to have to spend some time looking for sports arbitrage opportunities, they won't just fall into your lap! At first it'll probably take while to get used to this type of activity, but after a while you'll get better. If you have a couple of hours per day free then you'll probably be able to find a few arbs. However if you plan to make serious amount of cash then you'll need more spare time.
Be well organised
You're going to be placing numerous large bets with different bookmakers on events that will be settled (you winnings paid) at all different times. You need to remember (or better still record) all of your transactions so that you know where your money is. You will need to request withdrawals from each bookmaker once your winnings have been credited to your online account.
General sports and betting knowledge
Various websites claim that you need no sporting or betting knowledge before starting as a sports arbitrage trader. That's partly true. But would you invest your money anywhere where you don't have a clue what's going on? It's not a good idea!
Contrary to what you might hear, you should have some prior sports and betting knowledge before engaging in sports arbitrage. When you're talking about staking large amounts of money, you should know some basic things about the sports you'll be betting on and what the different types of bets are.
Internet access (broadband will help)
Of course you'll need internet access to access the many bookmakers online. Broadband internet access is a definite benefit because the sites will load faster and the whole process of researching odds will be a lot faster.