I think wealthy politicians are probably less prone to a straight up cash bribe in return for something, but they also have far more complex financial holdings and business dealings in which they might wish to have an unfair advantage. No one thinks they have enough money, no matter how wealthy.
It doesn't matter whether a politician is wealthy or no, I think they are all prone to corruption due to their roles and opportunities. I think a wealthy politician is just as likely as a politician with less money to commit illegal acts for financial reasons. It would be a mistake to think otherwise.
I do not believe wealthy politicians are less prone to corruption. I believe some people are greedy and corrupt because of their love affair with money, no matter how much they have, it's never enough. I believe this is obvious when you have the 1% complaining about paying their fair share of taxes.
If anything, wealthier politicians know how to hide corruption from the authorities. With larger cash flows, it will be hard to uncover what is corrupt and what isn't if wealthy politicians have a lot of money come into their personal coffers. Corruption is just like any other crime--if someone wants to get away with it and not get caught, they can.
It all comes down to morals and weather or not the politician has strong values. Both a wealthy and not wealthy politician are equally as corruptable if they lack the values and morals to understand that they have been corrupted. Remember everyone has a price at which they will allow corruption, the ones with values will be a much higher price.
No, I think that the ones who have less money would not be as prone to try to get bribes and things, since they have not spent their whole life just trying to get a lot of money like the rich ones have been doing. They are rich for a reason.