It takes a team of 2 people 6 months and 25K to set up a broker-dealer, do relevant background checks, pass relevant exams, pass audits, get personnel exemptions, SRO agreements, etc. (https://www.sec.gov/divisions/marketreg/bdguide.htm). That's a one-time process and WeFunder may have done it already.

Once that's done, setting up separate legal investment funds is a 1 month initial process (and its fairly simple to scale this up -- the individual investment funds would be set up in parallel). There's some quarterly paperwork and some yearly paperwork, but it's entirely within the abilities of one person to handle "dozens"