IIRC the idea originally was that Congress would be "citizen legislators;" ordinary folk who served out of a sense of civic duty. At least that was the concept floated! Of course from the beginning only fairly wealthy people could take several months away from their occupations. Thus in the main only the wealthy could afford to serve, not only in Congress but in the various state legislatures. How many teachers, librarians, auto mechanics - to name but a few - do you know who serve as elected officials above the local level? Even at the local level how many teachers have the ability to attend meetings and conferences during school hours?

Should an "average Joe" or Jill be elected to a state legislature or, god forbid, Congress, he/she would be forced to scramble for funds for re-election many hours per day, as Steve R above notes. Having a Congress TRULY representative of the population, at least in terms of occupation and income, is virtually impossible as the system is currently constituted.

People should not suffer finacial hardship by serving but niether should they be made wealthy. The Senate was designed as an upper house, hence a 6 year term. The house was designed to encourage citizen legislators, serve a term or 2 and return to their"real " jobs. So as to be closer to the public. But we have develpoed a "ruling class" almost a royalty that actively discorages average folks from serving. Hence part of the reason for the hatred of Trump among that ruling class.