What free genuinely covers
Salary benchmarks, company research, interview formats, role expectations by level, resume principles, negotiation theory and a large volume of first-hand switch accounts on public forums. Peers and former colleagues will also review a resume if asked directly. For direction and market awareness, free material is sufficient and often better than paid summaries of it.
Where free reliably stops
Free advice is general by construction. It cannot tell you which three lines on your resume are costing you callbacks, why your system design round keeps stalling at the same point, or what your specific leverage is in a live negotiation. Peer reviews also carry a politeness bias that removes the most useful feedback.
A sensible order of operations
Read widely, apply what you learn, and measure callback rate over a few weeks. If applications convert, you needed information, not coaching. If they do not, you have isolated a profile-specific problem, and that is the point where paid feedback is worth its cost rather than a substitute for effort you skipped.