"Doctorate in Clinical psychology, Median $66K/yr." Return on investment isn't very good there
"2. Master Plumber (90th Percentile Pay: $102,000; Median Pay: $60,000)
As long as we want running water in our homes and business, plumbers will be in demand -- job-outlook forecasts for plumbers are usually very favorable. Whether they work as sole entrepreneurs or for larger companies, plumbers typically spend their time installing and repairing water, waste-disposal, drainage and gas systems and related appliances.
There are many paths to becoming a master plumber, but a common one is through a term of apprenticeship to another master plumber. According to the BLS, most plumbers, pipefitters and steamfitters get their training in jointly administered apprenticeships or in technical schools and community colleges. Most states require that plumbers be licensed; licensing requirements vary, but most localities require workers to have a minimum of two years of experience and pass an examination on the trade and local plumbing codes."