As you can see by the responses, there are wide and varied uses for an air compressor.
I own two of them. One is a 220 volt high volume compressor that set me back a bunch when I bought it, but can run tools and sanders and is a great unit.
But.<font color="ff0000">•</font><font color="ff0000">•</font><font color="ff0000">•</font><font color="ff0000">•</font><font color="ff0000">•</font> is not very portable, requires 220 volts to run, which limits the heck out of where I can use it and it is big and fairly heavy (I think it has gained weight since I bought it, or at least my back says it did)
The other is a pancake compressor which I use 90% of the time pumping tires, using smaller air tools, tho it will do a 3/8 air wrench pretty well, and is highly portable for painting and just moving around to blow out sprinkler lines, etc.
So you see, buying one isn't going to likely be the perfect unit. It is either too small and noisy or too big, expensive and not very portable.
I recommend based upon your dollar limit heading to one of the Chinese box stores and looking for a porter cable pancake, and then picking up a few simple air nailer's, and sprayers to match the use of the unit. Get extra lines to stick together so when he wants to use it to blow the eve's clean he can do it.
Then let him buy the super duty unit somewhere down the road, if he see he needs it or gets the whole garage piped for compressed air.
No doubt he will then go buy you that nice diamond ring you have been talking about for .....many years.
This will improve the economy significantly whereby others will be called back to work, further stimulating the economy, which will spur on the recreation industry causing more sleds to be bought, and more snowmobile trips to be made, thereby keeping more businesses from closing all across the UP, and everyone will be happy.
And you thought this was a really hard question??? Humpph!!