Don't. Say something like "I want to keep x% of the company". Thus if you end up getting more funding than you initially expected (happens often) you'll essentially get a higher val.
It may be common but the more important question the investor will have is how soon and for how much you can sell the company (in other words how will you use the funds to create more value / reduce risk in the startup). There will be other terms associated with a funding that will have a significant impact on how much you make when you sell (for a reasonable range of exits). A couple of good sites for background on funding:
you're right, what I should have written is the question in their mind is "how soon and for how much can we create liquidity" with more of a focus on how much than how soon. In other words, how will the funds be used to reduce the risk in the startup. If acquisition is your likely exit (and that's a safe bet for most new startups) then they may ask you to speculate who would buy the firm and for how much. I am not advocating a "built to flip" strategy" as much as trying to understand an investor perspective.
