It would be great to know how many companies have already incorporated before applying to YC, and what their structure looks like (C-Corp vs LLC, split of owner

It would be great to know how many companies have already incorporated before applying to YC, and what their structure looks like (C-Corp vs LLC, split of ownership, etc.). Myself and different friends have started our own companies recently and we're going through this sort of thing for the first time, and we wish we had better information. When YC visited NYU in the Fall I asked a similar question and was told that registering as a C-Corp through clerky was the way to go, but it was already too late for us (we're an LLC). Now I'm curious what it takes to go from LLC to C-Corp, or if it's even a big deal this stage in the process.