One way to get good rakeback deals from the pokersites is to sign up as a proposition player. Not all pokersites use proposition players and it´s a secret which sites that does.
A proposition player is a player that get good rakeback deals in return for being a game starter. The proposition player shall start new tables and play at levels and games that need to attract more players. Even real casinos use proposition players, at least they did before. The idea with this concept is that many players doesn´t like to be the first who sits down at a table, and that´s where the proposition player comes in to start new tables to make sure these players doesn´t leave the pokerroom when the tables are full.
If you wan´t to be a proposition player you almost always sign up via a third party affiliate that has a deal with the pokersite. The terms and conditions for proposition players varies between the pokersites, so does the rakeback deals. Some offer up to 135% in rakeback, and other just 70%. Some pokersites just want proposition players for games at a specific stake level, which then make the proposition player obligated to just play games at that stake.
As you see, being a proposition player can be profitable if you get a really good rakeback deal. If you are interested in becoming a proposition player, also called a prop player, then make a search on google and you will find affiliates that offer deals with pokersites.
I have never tried to play as a prop player, but I´ve heard about non winning players that becomes winning players and make profit or break even when they play as prop players with a rakeback deal over 100%.
Remember that all proposition players gambles with their own money. You won´t get any other payment or gambling money from the pokersite except for the rake back.