Those looking to buy followers can have a hard time finding real followers, this is because most people who sell followers, are using fake bot accounts to follow you – anyone with a little programming experience can do that, so you likely don't want to deal with these people.
It can be very hard to tell if the followers you get are real followers, especially if the seller is not explaining to you, exactly how these followers will follow you. Some will likely advertise that they are selling real followers, but how exactly are they doing that?
If they ask for your password, you should be aware that they might use methods that can get your account suspended – or they use existing services, such as twiends.com to obtain these real followers.
Buy real twitter followers with twiends.com
Ok. You won't actually be buying followers directly, but you will be buying seeds, which are then offered to other users in the twiends network. People are willingly following you, but the only reason why people are following you, is so that they can get seeds to spend themselves – usually anyway. They also tend to unfollow you after some time, which can only be avoided to a certain degree; but there are also many users who keep you in their network.
See also: Buying Seeds From Twiends.com
Buying followers forbidden in twitters terms of service, but so far we have not yet heard about anyone getting into trouble from using twiends.com – likely because its a quality service – its not really effecting twitter negatively, unlike those selling their fake followers.