Is this legit? And without being a dealer how many cars can I bid on and how often?

Go to their website, it explains the process. What, where and how many cars you can buy is governed by state law. Also, if you plan to rebuild a salvage car you need to keep all receipts. This will be needed to register the car as a rebuilt vehicle. Again research your state laws and watch the copart videos on YouTube

Yes it is legit I don't know what their stipulations on building but I do know that a lot of your copart's have bidding on certain days of the week. There's also online where you can bid at multiple locations. I used to be a long hauler and I used to pick up motorcycles and cars at copart and IAA.