I mean, savings accts are paying 2.2 percent right now, and while it's a drop in the bucket compared to senior developer wages at AMZN, you're looking at 20k in interest accrued annually, which is basically what each of my parents live on in middle America.

Depending on where you live, who you support (or are supported by), and how capital intensive your independent business is, that could be plenty. Plus, you've already got a book deal worked into the business plan it seems.