So long as the sale of the real properties that you are inquiring about is by owner, then you need not worry about any issues with respect to the department of real estate in the various states that that you wish to sell properties. The department of real estate in the various states in this country oversees and regulates licensed real estate agents.If you own the properties that you wish to sell and wish to advertise online, there should be no issues precluding you from doing so. However, you would be subject to the laws of each state where the property is located with respect to disclosures and the like usually through a written document (examples, transfer disclsoure statement, carbon monoxide disclosure, and the like).