sec. 226(1) states that only a CA as per CA Act 1949, can be an auditor of a company. now as per sec. 2(2) of CA Act only a "member in practice" can offer such professional services. so only a member in practice can be an auditor of a company in India.
and as regards disqualifications, sec 226(3) specifies five clauses or five categories of "persons" who can't be the auditor of a company.
pls let me know if you have any further doubt in this issue..