A small but growing number of private firms practice public interest law. Such firms work for under-represented groups or specialize in issue-oriented work, such as civil rights litigation, tenant advocacy or representing whistleblowers. Most of these firms have relatively small staffs and some charge fees on a sliding fee scale or maintain a traditional private practice in order to fund public service ventures. Full-time openings for these firms tend to be somewhat sporadic and very competitive; usually a few years of relevant experience in the public or private sector is required. Starting salaries in private public interest law firms generally range from $50,000 to $70,000, though some can be considerably higher.