I think you should always choose what you think are the most interesting or valuable questions from any source, but perhaps prioritize subscriber submissions in the interests of reading and/or answering time. I'm looking forward to this!

I think you should use your discretion on the questions and source. It's your newsletter, after all. Perhaps give subscribers preference, but if I'm reading the stuff, I'd rather have the most interesting questions and answers, rather than the ones people paid for.

I think it's a good idea to have questions open to paying subscribers. Kurtjmac of Far Lands or Bust! fame (http://farlandsorbust.com/) does so; he answers donators' questions while recording episodes.

As I'm just starting out on my own entrepreneurial journey, what would make this interesting to me is just that: How to run a business, and maybe make and sell apps (my pipe dream) etc. for a living.