Rule 506(b) permits an unlimited raise from an unlimited number of accredited-investor buyers plus up to 35 sophisticated non-accredited ones, provided there is no general solicitation and existing relationships are used. Rule 506(c) allows open advertising but every purchaser must be accredited and verified with documents, not just a tick box.
Issuers file a short Form D notice with the sec and pay state notice fees. The securities are restricted and resale runs through rule-144 or another exemption.
Because disclosure is minimal compared with a registered offering, these deals rely on the buyer's own diligence. Antifraud liability under rule-10b-5 still applies in full, which is the main protection an investor actually has.
Related: accredited-investor, qualified-purchaser, rule-144, securities-act-1933, jobs-act