Theil invested 500k when Facebook had 9mn users. If you have that, you can raise way more and faster.
Historic examples don't help.

If you don't have anything developed, you can give away up to 15%, but the days of investing in companies who don't have a product market fit are pretty much over.
Only the hot spaces.

Just remember equity is a form of value exchange, always remember if you don't like the numbers you hear, negotiate. Sometimes, you don't know what you can get if you don't ask, that goes for both parties. However, since you do not have a product and don't have real numbers, even small-scale, your risk perception is likely very much higher, so to an investor coming in their money, currently (high value) versus equity in your company at current stage(high risk), equal a higher equity percentage, due to value perception. Risk/Reward factor! Reach out to me if you need more help!

I would ask myself what this angel/investor put on the table except for money. If it's just money, you can use some evaluation techniques to calculate how much he deserves. If you think he will promote to the company other than its money, I would build an equity structure that will make it happen. I have some concepts in mind, we can further discuss it.