Before finalizing the buy, I would very highly recommend that you do a compression and leakdown test for every cylinder. This should very quickly tell you how badly the engine has been abused.
You can do the tests yourself if you know how (and buy a $30 gauge) or any competent mechanic will probably do it for $40 or less.
Find out what the acceptable numbers are beforehand (try asking around the crx forum). If the engine doesn't push those numbers,
do not buy it, even if you plan a full rebuild - too much other damage may have been done that you can't see.