Early stage startups, no. They don't typically know what to sell, how to sell, or who to sell it to. Many failed founder sales efforts start out with wishful thinking "I just need to find someone to help me sell." Pre PMF founders will drive you crazy with their naïve sales/product decisions.

However, for a company with PMF, if you have industry connections, and can help them get a short term boost of deal flow, I could see that being very attractive.

Helping first time founders setup any sales process at all can also be viable. You help them refine their closing process, hire on their team, and then move on.