Ask your library for microfilm of the "Atlanta Daily World", Black Americas only daily newspaper of note. Ask if they have city directories for those years. Call the main branch of the Marietta Public Library and ask the geneal/hist librarian to look up the surname you're interested in a 1920 city directory. He/she may mail you the Xeroxed page your relative appears on for no charge.
Hope this helps,

Bijan C. Bayne