Adding another bathroom

Now that my son is past that stinky boy phase, he's now more interested in maintaining his hygiene! It's great, but we have limited bathroom access due to the increase in usage. I'd love to add another full bath! I have no idea where to begin, though, and am looking for recommendations for someone that can help walk us through the process and provide a realistic quote. I have additional projects that I'd like to work on, too, so this could lead to additional jobs.