I need a buffer--Recomendations?

Just like the title says. I need a floor buffer. I need recommendation for;

• Brand
• Speed
• Weight
• Size
• New or used?
• Price range new
• Price range used

Going to use it for several things;

• Rug shampooing
• Encapsulation
• Pre-agitation
• Hard floors
• Bonnet
• Videos

Well that's I can think of now. Any recommendations?