Best place to buy a compressor, or for that matter, a myriad of other items is
www.harborfreight.com.
You want an
oil lubricated compressor, period. Imagine, your Cobra engine, or any engine running on polymer coated parts ONLY; no
oil!? So why would you buy a compressor like that?
Agree with the dual stage vs single stage setup. More efficient.
You need to look at the air pressure (PSI), and air consumption (CFM - cubic feet per minute) requirements of the tools you own, or plan on using. Then size your compressor to meet the demand of the tool with the highest air consumption.
Next, you have to assess the electrical demands of the compressor. Up to about 2HP, normal 110VAC will do. Since the garage is usually where your electrical distribution panel is anyway, wire a separate 30 amp breaker to outlets just for the compressor and electric tools in the garage. This way, the (normally 15 amp) breaker doesn't pop when the compressor is running, and your spouse turns on the microwave or toaster. Over about 2HP, you'll need to install a 220 volt outlet to run the compressor. Make sure your home has 220 volt service before you buy the compressor. If you have an electric stove, an electric drier, or central air conditioning, you have 220 volt service running these appliances. You can tap your compressor outlet off the 220 volt distribution for these appliances.
My needs were quite minimal, a 1/2" air impact, and 1//4" air ratchet, pumping up tires, and cleaning parts. The $199.95 contractors pancake style 110v from Harbor Freight worked just fine.