You will get alot more responses if you go to the Mazda part of the forum and ask that. Thats where the rotaries are at.
If you get one before you buy it check the compression. If the compression is bad dont waste your money you will be putting alot into it later.
Expect repairs, have a decent amount of money set aside for repairs. Even if you do it yourself you still gotta get parts which sometimes dont come cheap.
If you are ablet o have spare parts keep them. You will probally need them later or know someone that will.
These things eat oil like theres no tommarow. ALWAYS keep oil with you in your car. I usually keep breakfluid as well, since ive had bad luck with my clutch.
When you buy one ask when was the last rebuild. If its been 100k or more, you may be needing one real soon, or you may not it depends on how well it was taken care. off.
Parts are hard to come by sometimes, most autopart stores dont carry what we need. Ebay is your best friend for this.