As a young assistant professor (female) in a math-oriented field, I've looped in a former colleague, now in industry, in one of my projects. While he is professional and skilled, a pattern has emerged where he initially expresses a 'happy-to-help' attitude but later requests unrelated academic favours, creating an unspoken sense of obligation. Although he self-invited himself into the project, his actions are giving me the vibe that since he agreed to be in the project, I owe him favours. I am now afraid that this may persist, and if I do not oblige, he will be negligent in his part of the project. Since he is a consultant, not my research assistant, my leverage is limited as the PI. Given his impressive skills, should I proceed with the collaboration, or are there alternative strategies to navigate this situation?
Edit: He will be a middle author in the paper. In my field, author order matters. Also, I worked with him while he was a PhD and I was a postdoc under the same advisor. He was subtly showing this pattern then, but not strong enough for me to hate him. He was generally very well-behaved with our common advisor, who I believe protected me back then.
Example of unrelated favors: help in doing some of his works in other joint projects.