What you must know is that where ever there is money there must be disagreement between two parties or entities just to make sure one gains more than the other for their selfish gain and interest, that could also leads to bribery & corruption, conflicts as you said but with good quality control towards one another base on their educational background they may control their interest of greed towards the money. For instance; taking example from my country Nigeria how we have bad leaders and they don't care for her citizens whether things are fair with them or but immediately they are sworn into Power as President, Governors or whatever position they may decides to be, it turns to self interest because there is money involved in that particular position so, greed shows up quickly.
Just like they always said that money is the root of evil that is the real truth about it, because no matter how good someone might be once he or she involves into money their most likely be a changes. Though, that is the main reason why most people normally end up not sticking to their words, more especially the politicians after achieving what they want from the citizens they would lock up an turns their back on people that gave them opportunity due to selfishness and greed. So however, I think is quite obvious right now that whenever there is money between two parties their most likely be a disagreement, because one of them would definitely want to overcome the other just to satisfy their selfish life.
It is not only the politician because those you call politicians are just ordinary people like you and I, they are not created differently. What I know is that there is an inherent greed in humans that always strive to manifest at every given opportunity. It is this greed that leads to most of the negative behaviors and disagreements we see here and there. Even the wars you see here and there have everything to do with money and power and as long as money is involved, there will always be disagreements.
However, some people have actually been able to reduce their greed to acceptable level which we can regard as putting it under control, hence the reason you can trust them with money and do business with them without much worries.