Legal Question in Real Estate Law in California

Not sure from the brief statement of the question exactly what business activity you have in mind, but it's probably "legal" in principle, with a strong possibility of becoming illegal unless careful attention is paid to full disclosures, etc. etc., and if the leases involve real estate, a license would be necessary unless you are dealing with your own property, in which case a broker's license might not be required. Consult a lawyer in person, and be prepared to describe the business in some detail!