From my experience founding companies, you've gotta commit 100% to it to have any chance of success. That doesn't mean working on an idea in your free time. Consider the fact that someone, or even a funded team of someones, are out there putting in 100% effort to solve the same problem. How are you going to outcompete if you're working on this problem in your spare time (which I imagine is quite limited having a wife…
An alternative version would be to spend the first months trying to sell the product to customers even before it exists. Try to validate as soon as possible, then build and deliver the product.