Being rich is not a sin and does not disqualify a preacher from preaching and teaching. But if the motivation is to make money and increase wealth by his preaching, then that is quite different and such a preacher would not be working with the Holy Spirit.
Rich or poor, if a preacher is not making the death and resurrection of Christ his foundation of preaching and teaching, and "determining not to know anything except Christ and Him crucified, he is preaching another gospel and is not supported by the Holy Spirit.