Ask HN: How hard is managing the commercial side of a contracting business

I'm interested in going independent and starting a small software contracting / consultancy doing business applications and application modernisation work. I've got former colleagues who want to work with me, and we've got over a decade of experience each on the good, bad and ugly of this type of work.

I'm confident we could execute on the technical work, but the commercial side worries me. My current employer deals in smaller deals and in the past year I've seen

* Non payment * Bullying by customers to try and get free labour * Companies deliberately under bidding at costs they know they can't achieve * Customers using ambiguity in statement of work to extract extra work (for example the word "secure" causing a lot of private endpoints, HSM keys and Microsoft Defender needing to be configured for a recent Proof of Concept piece of work)

I've also seen some good clients and companies I'd like to continue working with. I'm concerned that the bad customers take up 90% of the time.

From people's experience, how tough is the commercial side of this sort of business? Do you need a hardened commercial guy to succeed?