Well, do YOU really want to go with this business opportunity? That's they key, what do YOU want to do, not this alleged angel investor. I would be weary when "investor" approaches me first and them asks me to do a lot of work. Why? I think you need to figure out what YOU want to do first, evaluate business potential of the idea at hand and not bend over backwards trying to change your communication style.

Now, back to communications with investors. They almost never say no, but silence is very common. Silence can be interpreted in several ways:
- they are simply not into your business plan
- they are way too busy to respond, which is very common
- they want to keep getting updates from you for several months before they meet you again F2F (common)

http://www.anagard.com/blog/2015/01/13/venture-capitalists-advice-to-startups-how-to-successfully-raise-funds/ You can read in my article more about this topic and focus on communication segment of the paper.
Good luck, and call if you have more questions.