Sadly, after more than 20 years building software, _NEVER_ trust a business person. My faith in humanity had to have me bitten by this the hard way more than once.
1) Never assume people will respect the value of your time and the fruits of your labor. Some people in particular are looking for related arbitrage opportunities. It isn't even necessarily malevolent, it can be just a frequent human limitation in how value is perceived. Though sometimes it is predatory to the point of malevolence.
2) Assume any future promised reward is unlikely to materialize when making your decisions (if it is not specified via contract, assume it will outright not happen). If a given course doesn't make 90% sense if a possible upside doesn't happen, then it doesn't make sense.
When I see business people smile at each other and shaking hands, I cannot make sense of this in my mind. What's the point of smiling when both people couldn't care less if the other person dropped dead on the spot.
https://www.ribbonfarm.com/2009/10/07/the-gervais-principle-...
1. Do not trust “business” guys! 2. If they give you some “sweet” offer, look at the rule No.1
Lumping it all into "business person" isn't very useful because there are a lot of business people. So maybe a few specific examples can help.
Account managers and salespeople: while their stated job is to help you with customer issues, they're actually paid to sell/upsell you, and even if they're not, they're evaluated on selling/upselling you. This means they're likely to stretch the truth about the product they're selling in order to close the deal. So when you're interacting with salespeople, you can never 100% trust what they tell you, because they're not actually trying to help you.
Business development: the company they work for has an agenda. That agenda won't be obvious to you. Maybe they're asking you to come in to do a demo because they want to consider partnering with/acquiring your startup. Actually, they're spinning up a team to just build it themselves, but they want ideas. The problem is you have no way of knowing which is which.
HR: you know the common wisdom, they're there to protect the company, not you, and often that makes a huge difference.
Someone hiring you for contract work: they do want the work done, but they're trying their hardest to avoid paying. That means every ambiguity in the agreement becomes something they might try to leverage against you.
In other words, don't trust someone until you understand their hidden motive. "Business people" just tend to have more of them than your average person.