When you invest in somebody, work with somebody, or start a company with somebody, you're signing up to spend the next decade of your life having them in your life. You have to make sure you genuinely like these people, and you don't consider it work to have to answer a phone call, take a meeting, or spend time with them. If it's exhausting, if they're downers, if they're negative, or if they're difficult, no amount of money is worth it.