As a former successful realtor, I think you're nuts. You studied for your PhD and I believe you will make more money in the field you studied for than in real estate. Real estate sales is a very expensive field. You will be required to pay brokerage fees, legal fee, MLS fee, marketing, advertising, gas, etc. Also there is NO GUARANTEE of a paycheck. You get paid at the end when you close a deal. This means you can spend months with a buyer or seller and receive $0 in income. You will have to live off your savings or have somebody else pay all your expenses. Understand you are essentially self employed and starting a new business.
On the other hand if you had a full time job in the field you studied for, you would be receiving a weekly paycheck and no out of pocket business expenses.
If you insist on working in real estate, pick the company that has the better training, great technology tools and software, marketing tools for agents, etc.