Legal Question in Business Law in California

I would say that since both the real estate and the auction businesses are licensed and regulated, the first step is for the proprietor to acquire the licenses. I don't believe that the business operating "online" reduces the need for licensing. There will be additional requirements as with any business, including a requirement to keep books adequate to support determination of profit and loss and the preparation and filing of accurate tax returns based upon those records. Finally, as with any business, the owner needs to select a form of business entity (or "none," if it is to be a sole proprietorship) and take whatever steps are necessary or appropriate to the formation and operation of the entity (corporation, LLC, partnership, etc.).

Way too many to list. You need to retain a good real estate attorney, who will probably also hire tax, licensing,, administrative law, corporate formation, and other specialists in order to keep you out of jail and civil suits.