I'm glad to see you included a more realistic 7% average return scenario, since 11.5% is highly unlikely when you consider stock market returns over the truly long term (say, 1926-2020). Your 8.7% case is more realistic, but when you adjust for inflation, it's still higher than history would lead us to expect.

As for the flipping or reselling aspect, I'd be curious to see what that includes. If you would give examples of what type of items you flipped, where you sourced them, how you sold them, and how you determined your pricing, that would provide tremendous value to your readers, far more than a few simple compound return data making the (correct) case that investing over the long term should be a major part of most people's financial plan.