Congress consists of 500 people and each year 100 are replaced in a draw of that lottery. Members of Congress get $1m a year, tax-free, for the rest of their lives. In exchange they have to be representatives for 5 years and are strictly forbidden from ever making money any other way ever again.
No salaries, no donations, no gifts, no handouts, no speaker fees, no nothing.
Any downsides (representatives no longer answer to their voters --- hahaha that was a good one) are more than compensated by the limit it puts on corporate bribery.