Were there wealthy people in the Corinthian church?
Yes. The Corinthian church included well-to-do members. They demonstrated their wealth when they mishandled the Lord's Supper by bringing expensive foods and wines, while Paul chose not to burden them financially and instead received support from the poor Macedonian brethren.
Les explains that there certainly were well-to-do people in the Corinthian church. He notes that they revealed this when they goofed up the Lord's Supper by bringing their expensive food and wines. Paul, however, spared those who could have afforded to give him money and instead took support from poor folks up in the mountains. Later he says the brethren from Macedonia—Northern Greece, poverty-stricken Greece—supplied what was lacking to him, so he kept himself from being burdensome to the Corinthians. This shows the Corinthian congregation included wealthy members, yet Paul did not rely on them for financial support.
And when I was present with you, and wanted, I was chargeable to no man: for that which was lacking to me the brethren which came from Macedonia supplied: and in all things I have kept myself from being burdensome unto you, and so will I keep myself.