Re: First Time Build - I welcome advice
It's cool that you're building this out of personal loyalty/gratitude for a friend. That alone will keep us interested. Plus we'll be interested in how your friend does with it. So stick around and keep us updated, won't you?
With a chain driving the rear wheel you won't be able to make the bike easy to pedal when the engine isn't running. Though at one time at least one guy was making and selling a dis-engagable rear drive sprocket. But I haven't seen or heard of him in a while. And I've seen no others. So I suspect that this is something that didn't work out. But that probably won't be a deal killer. With your mechanical abilities and a Honda engine, you should be able to keep breakdowns to a near-zero level. It might take a bit of learning your particular bike/engine/drive train combo. But it shouldn't be a big problem.