It's crazy how some people here will just make all the assumptions possible in order to refuse to believe you. Anyone who's used a good model with open code or equivalent will know that it's plausible. Refactoring is really cheap now when paired with someone competent.

I'm doing the same as your co-founder currently. In a few days, I've rewritten old code that took previous employees months to do. Their implementation sucked and barely worked, the new one is so much better and has tests to prove it.