Developing / Choosing a Niche - Looking for Resources - Focus!

[Steven Segal]

I have a friend who is getting started in real estate. I just had a lengthy discussion with him and how he was running a bit thin. Additionally, his current practices aren't scalable. 

Does anyone have any good resources for any of these topics:

• Possible niches in real estate investing
• Perhaps pros and cons of bullet pt above
• The importance of focus (already told him to read The One Thing)
• Anything else that seems relevant to the topic. 

TIA for the insight. 

Steven