What should we prepare for in terms of IP before talking to an investor?

This question is like how long is a piece of string ... it depends on your sector, business strategy and commercialisation pathway. Generally worldwide patents is expensive (there are time constraints), trademarks are mostly straight-forward, and copyright a matter of documentation. Depending on the stage of the company, the due-dilligence may reveal what they think needs to be secured to an adequate level of the amount invested.

Some off-cuff observation might be you tell them did X in core markets of Y but if given Z $$$ can do XYZ to show them you know what needs to be done but also careful with what is spent so far. If you can't relate IP strategy to business (should have been trashed out early) then you are in more serious trouble than you realise (eg may be barred by statute from patenting).