Ask HN: Advice for consultants/freelancers, rather than start-ups

I've found a lot of interesting advice on HN specifically geared towards start-ups (e.g. assembling a pitch deck and venture capital deal structures.)

I'm wonder if the community can recommend any resources (books, blogs, forums) that have advice geared more towards consultants/freelancers (dev. shops, design firms, social media/online advertising agencies). Somewhere with topics like how to do sales of services (rather than products), contracts, hiring/outsourcing, accounting, etc.—all of the things I imagine they teach in business school.

Thanks!