Value proposition is clear. Anyone with a big enough following can host a Q&A section where they get paid to answer questions.

I would not use the app as a host. If I'm going to host a Q&A, I'd rather do it somewhere where my followers already are such as Twitter rather than having to try and direct them to a new channel. I prefer my answers to be at a place where as many people as possible can see them (again, Twitter is a good example). I'm not interested in making a few cents off my followers. I'd rather do a free Q&A, grow my network/influence, and monetize later on by selling products etc with high higher margins.

I might use the platform if you could get some amazing people on there which I couldn't reach otherwise. For example, if I could ask Tim Cook and get an answer I'd pay for that. But I can't imagine anyone like that doing a Q&A for the money.

I don't believe in this model, but I might be wrong! So take my feedback with a grain of salt. I would focus on trying to prove/disprove the model. Everything else is secondary.

Here's how I would try to prove/disprove the model: find a handful of people that are open to doing a Q&A like this and for which you think you can reach a decent sized audience willing to pay to participate. Figure out the simplest product to test it out with them.

In other words you don't need a sign up flow for Q&A hosts, etc. You could even hardcode separate pages for each. For tipping/payments, come up with something that you can execute as quickly as possible. Maybe that means not tipping per answer, but just a flat fee for access. Use Disqus for Q&A. Etc. Simplify things a lot so you can prove/disprove the model as quickly as possible. Get real user feedback as quickly as possible. Iterate based on that.