You can buy a NEW 10 HP rotary converter from Anderson Converters (AZ). Google for them online. If you can find a used 10HP 3 Phase motor, you can add a panel sold by Anderson for $259 and have an inexpensive rotary. A used 10HP motor should be able to be found for much less than $450. I paid about $50 for the last one I bought.
I wouldn't even think about using a single phase motor. Three phase motors have more torque, and you need it for the Nazel hammers to get started (whether or not you unload the compressor).
The advice you are getting here is good advice. It's based on experience. Don't just smile and discount it. If you are not extremely mechanical inclined, and don't already have a means to move heavy equipment around, or something to safely hoist (and move) hundreds of pounds with a high overhead clearance shop, you are probably going to have to spend a lot more than the "dreaded" $13,000 you are thinking about. Incidently, if you are patient, you probably could find a working 2B for well under $13,000 anyway. You need to look though, it isn't likely someone is going to send a good deal your way out of the goodness of their heart (it has happened, but I wouldn't hold my breath).
Then again, if you are mechanically gifted, have a means to move heavy equipment and parts around, have a high overhead clearance shop, and some machine shop equipment (and experience), you might end up with a working hammer for a couple dollars less than $13,000.
How do I know these things....? Experience.