"oil-less compressors" - in my mind, *universally* a bad idea. It almost always implies a diaphragm- or bellows-type pump. Neither is durable or powerful, regardless of the HP rating of the motor.

I hearily recommend a belt-driven, piston-type pump compressor. This type allows you to replace or rebuild individual components. Anything less is just a toy.

Look at ratings in SCFM, not HP. That's Standard (temperature) Cubic Feet per Minute. Then look at the requirements of tools you want to buy.

I use a 6hp, belt-driven, oil-lubricated compressor, rated at 10.5 SCFM at 90 psi. It is a 220v motor, but I was fortunate enough to have the 220v service entrance to my house located in the garage, so it was easy to drop a 220v circuit. I paid $225 for mine, second hand, and the seller threw in a bunch of accessories.

One bit of really good news for the DIY painter is that modern HVLP (high volume/low pressure) spray guns are a whole lot less demanding on a compressor than the old-school guns.