Corps that have R&D agents are as follows;
- Amarr - Carthum Conglomerate, and Viziam
- Caldari - Ishukone Corporation, Kaalakiota Corporation, and Lai Dai Corporation.
- Gallente - CreoDron, Duvolle Laboratories, and Roden Shipyards
- Minmatar - Boundless Creation, and Core Complexion Inc.
The RP you get per day is dependent on several factors. First is the level of the agent. They come in levels 1 - 4. The higher the level of the agent, the higher your standings must be with the agent's corp and faction. You must also have the science you want to researched trained. The higher your science level, the more RP you get. Lastly, the agent is sensitive to standings and quality. that means more standings = more RP. Also getting the social skills that affect agent quality and reputation up will increase your RP rate a bit. Now with pretty good skills and standings, and level 5 in the science, I'm getting 117 - 119 RP/day from level 4 agents.
To get more than one R&D agent you need to train Research Project Management. You get another agent each level. The last level takes forever though so even I don't have it yet.
R&D agents used to be the only steady source of datacores in the game. However, recent changes now mean that people can exchange LP for datacores at Militia agents. At the time of writing, the new system is so recent that the market is still fluctuating to reflect the change.