Legal Question in Real Estate Law in California

No, there is no limit. The only effect of having more people involved is that you begin to be subject to more and more securities laws and requlations the larger you get, and the more broadly you spread shares in the group. There are both state and federal securities laws that would come into play for any size group. though they are simple formalities for small closely held companies. They can become quite complex for organizations whose securities are openly traded, even if only in private transactions.