How should one navigate a "I currently do not have any open positions, that may change depending on grant applications" situation?

Question

A prospective postdoc PI, after looking at my application and papers, told me "I currently do not have any open positions, although that may change depending on grant applications", afterwards he invited me to give a talk at a fancy seminar at his department and told me my work is "very impressive".

Assuming that I am the perfect fit for this lab and that I deliver a good talk: How should I approach the issue of funding with this PI during my talk? What can I offer in order to convince him to find a way to hire me?

Answer 1

Without funding there is likely no way he can hire you. It isn't a matter of convince.

I'd suggest that you give the talk. If travel is involved, ask about reimbursement. Ask him when you should contact him again when he might know more. If you give the talk and he seems impressed then good, but you can also, perhaps, use him as a resource for finding another position elsewhere. He might know of colleagues in the same field that might consider you and might be able to recommend you to them if his funding is tentative or far off.

He can't expect you to wait around, so has incentive already to keep you informed.

If the talk is in person, try to arrange a meeting with the department head to enquire about other positions that might be open or about to open. Make it a multi-pronged attack. Or "hang around" the department and talk to a bunch of people. Who knows what might develop.

Answer 2

What can I offer in order to convince him to find a way to hire me?

Probably nothing. It's already his job to find ways to hire postdocs.

You are approaching this backwards. Instead of looking for PIs and hoping they have suitable funding, you should search the appropriate funding agency's grants database. Identify who has received funding recently. Then see if they are a suitable PI.