Experience in business, successful experience for at least some of the time is essential for politicians.
Career politicians who never do anything but politics are obviously geared to riding the system and corruption, which is bad for everyone except those with vested interests.
Ideally politicians should be required to raise ALL their campaign funds from the general public, say no donation over $1000 per individual. That way a big campaign would NEED grass-roots support in the truest fashion.
I had a hub, based upon an idea I had in 2007, that demonstrated that with enough cash, you can buy an election.
I was offered a 'safe seat' in Westminster when I was in my mid 30's when some bankers wanted to put me into parliament for them, "which party?" I innocently asked... "We don't care, you choose, we want politicians in all parties" was their reply.
Glad I never entered politics.