Clearly the man was joking, but we went on immediately after to discuss the illegality of fostering real estate transactions without being officially licensed AND having your license activated by a broker.I know you are not in the US, these laws may be different in your country, I just felt maybe this post may help another curious BP visitor understand the severity of the actions you're describing.Great Course, btw. 

The area gets 12+million visitors per year.

Vehicles may not be parked on the grass.Tenant agrees to advise their guests/visitors about parking and agrees to be responsible for improperly parked vehicles of their guests/visitors.Any assigned or unassigned parking spaces (or carport, if any) available for use by Tenant are limited to private passenger vehicles, and Tenant agrees not to store any recreational vehicle, trailer, furniture, appliances or any other property on said parking space or said carport without prior written consent of Landlord.Unauthorized vehicles or vehicles parked improperly are subject to tow.Tenant agrees to follow municipal code for proper parking on the street or elsewhere.VEHICLE REMOVAL.Without notice and without liability, Landlord may order removal of any vehicle from any parking space or carport which is unauthorized to park on the premises, is parked illegally or which remains inoperable for a period of fourteen (14) consecutive days.Any vehicle owned by Tenant and remaining on the property after the termination of Tenant’s right to occupancy may be immediately removed by Landlord with full immunity from damages for such removal.Tenant agrees to indemnify Landlord for towing/storage costs incurred.

If you want to rent for short-term stays (fewer than 30 days) in a place that is not your primary residence or you want to rent for short-term stays that will total more than 180 days in a calendar year, you can obtain a "visitors accommodation" license. 

I thought about putting a camper, RV or tiny house in my backyard to Airbnb out to visitors.

I live in San Diego-a destination city for many visitors.  

Out of every 100 visitors we should get 2 sales and/or 10 opt-ins My recommendation is to go the Facebook route of advertising..lots more targeted

Recently, her brother began coming over to visit or spend the weekend.

This will make it appear to the recipient to be a personal address, but it protects you from unannounced visitors at your door. 

Have you follow-up with open house visitors?