Getting 10 people responding to a newspaper ad, probably not fine.
There's two reasons why this isn't fine, actually: You can't get strangers to invest unless they're accredited investors; but also the newspaper ad itself is illegal ("public offering of an unregistered security" or something along those lines).
My post is about induction. Let me explain in detail:
It's OK for one person to invest in my startup.
It's still OK if I get one more person to invest in my startup. Induct on the number of people.
It's OK to get an infinite number of people to invest in my startup.
Q.E.D.
The reason induction doesn't work is because the law defines that a certain number of people is "public offering of an unregistered security". In math, there is no such restriction.
There's two reasons why this isn't fine, actually: You can't get strangers to invest unless they're accredited investors; but also the newspaper ad itself is illegal ("public offering of an unregistered security" or something along those lines).