@Susana Santos - Do your research and choose which area of real estate you would like to start a business in, as their are many to choose from. What area do you enjoy the most, flipping, wholesaling, rentals, a combination, etc.? Then, focus on the area(s) you chose and learn everything you can from BP and any other recommended area (BP is the best though, just my opinion).
Once your real estate focus has been chosen and you have gained the required knowledge to provide you with a sufficient amount of confidence, consider forming a Limited Liability Company to run all of your business transactions through. Always consult with the appropriate individuals to ensure you have followed all of the necessary steps to become an organization within the state you choose. If done correctly, this will provide a "level" of protection for your personal assets in case of litigation.
However, litigation is something you wanted to protect yourself from. So, once again, when you have selected your area of business focus, make sure your paperwork for all transactions in your business are legal, accurate, documented, tracked, and up-to-date at all times. Research different software products that can benefit your business, such as a financial tracking program and a customer relationship management program. Some are cloud based, some are installed on your computer, some are expensive, some are reasonably priced, and some are free.
Below are two sites from Nolo to learn more about forming a business organization:
http://www.nolo.com/legal-encyclopedia/limited-liability-company
http://www.nolo.com/products/form-your-own-limited-liability-company-liab.html
Feel free to contact me if you feel I can assist you with any questions you may have!