Playing poker online for real money can be a big change even for players that have been successful in real life home games. The first, and biggest, obstacle will be the rake.
The rake is what catches most players that are used to being profitable in real life poker. While it may seem like an insignificant amount, in reality paying the rake can turn a profitable player into a losing one.
Of course, players that have already played in real life poker rooms will be used to the effect of the rake, adn this will not be an issue. The next big change in moving to playing online will be the change in the interaction with the other players. without realizing it you may be used to picking up on the other players body language, and now of course that will not be available to you.
One further change that you may not expect and will have to deal with is the different social interaction of playing online as opposed to playing in the real world. While there are many benefits to being able to play poker from home, there can be some drawbacks too. It can get pretty lonely sitting in silence night after night clicking your mouse button. This is even more noticable if you are used to the socialness of having to go to a real poker room to get your game.
In my opinion, the advantages of playing online far outweigh the disadvantages but it all comes down to how the individual player feels.
If you are just starting out with poker online then a great room to try is 888 Poker. They have some great bonuses for new players and very low micro stakes tables for beginners.