buy and hold / flipping or wholesaling

[Michael Seutin]

On this thread I would like to know the opinions of professionals if a beginner or an investor with a few years experience wanting to make a living from real estate would be better off putting all of his energy into
- Buy and hold for rental income, or
- Wholesale properties, or
- Flip properties, or
a combo of each which would make someone probably less knowledgable in any one area.