I've thought about writing the same type of book with a broader scope. HR processes, what is a PEO, types of insurance and how to shop for them, accounting/bookkeeping practices, importance of contracts, how to collect AR, how construction contractors bill and how to ask them to quote, overview of electronic signatures, retaining communications from the start, what is a payroll audit, etc.)

I'm sure there can be some other great advice in there about not spending too much on design upfront, using graphic design templates as much as possible, etc.

The reality is a lot of the stuff that can really bite you in the ass (PAGA lawsuits in CA) you only learn about when you're about to get reamed.