Totally agree. Be very careful of partners. Over the years I had developed some strategies to say the ugly things upfront.

If the partner had bad experiences, he will appreciate what you say.

If this is his first time. Try not to scare him off by being to direct.

At the end of day, when partnership to split that day, the person in charge of sale say that he has totally no idea how the money is spend so much on expense (like $8000 unacounted for). Further scrutinised, it finally discover that he is taking these money and treat as “monthly salary” without informing the partners. And worse the debt was never pay through these profit but through the other partner. These business last two months.

So, the most important thing to learn is find the right partner with passion to grow the company rather than self-interest and too business-minded.
Business required win-win situation, not u-win-i-lose mentality. However, it is easier to say than done. Most partner is actually wolf in sheep coating.
When money is the issue, the moment of truth will come.

Secondly, no matter how time-consuming and how-stupid it look, always forged a agreement signed by both partners on job responsiblity and decision-making. Without these, everyone has every right to say what he wants and twist it.
The most common problem faced is this attitude of ”
I spend a lot of times making sales every day, travelling until cannot breathe, and you as programmer sitting in front of computer serving internet. And now you say I eat the money ?? I deserve the money for the hard work.”
And the programmer will shout :” So what did the sales do ? Travelling and getting as much sales and just throws the things to me to complete, and then you said sale is done. And that end of month, you deserve this money but yet no money is obtained from customer!!!”.

This is a true account unfortunately that happend to my friend.

So what happened is to find the signals that thing is going out of hand:
1) The other partner suddenly becomes busy in answer your call, and then say everything under control. No problem will be revealed to you. He try to keep everything short and hang up.

2) When ask about revenue and expense, he say he does not have time to prepare even though he promised in “few day” times. and days become weeks.

3) Both become suspicious of each other activity. Thinking that there is something to hide. Truth be told when you realized from other friends of his that he used to be bankrupty but never told you.

So no matter what people tell you about best friend or anything in business. Keep in control rather than pretend nothing happened. If something tell you nothing is right, it probably is.

If you read Apple Confidential book, even Steve Jobs cheat his partner by getting bigger pie of the profit without telling him so.
So no matter how close, how passionate, or how admirable a person is, do not be overly naive.