So... if I have this right, your C buyer's mortgage company will not allow a double closing with transactional funding because they see that you're not the owner of the property you plan to sell your C buyer, and it will take them about a week to do their due diligence after you buy it to see that you actually now (then) own the property. Why not just borrow hard money? I know plenty of people who would be happy to loan for a week versus a day. If you'd like to discuss this further, please feel free to give me a call at 817-300-1132.
Thanks, Robin