Remember that it can also send you to an early grave if you ignore the rules, tricks, guides and all that it takes to make you have positive and good results. Most assured way to win money betting sports is to work on a particular niche and monitor it carefully and regularly. What it needs is some good follow of the sports books you always do your bet at, its very important here. 

From my own experience and knowledge an underdog at home can be the best betting in sports. However you can see different types of betting websites and categories bellow:

However, there are free and paid betting sites.

Free betting sites: there are sports betting sites that does not require you to pay any money for registration, you sign up for free and will be required to deposit some money that you will use to bet.

Paid betting sites: these are betting websites that a bettor will need to sign up with a little or more fee in order to be a member of the betting club, and after that you shall be asked to make some little deposit for your betting, the amount may be ranging from $20 to $1000 depending on your budget and targets.