I want to buy a SLR camera, but I don't know which one to buy. Mainly used in commercial photography and some products. Is there any professional who can recommend me?

Or buy an entry-level 550D600D and so on. When you can play the entry machine to the extreme, your level is already quite high. Otherwise, buy a high-end Quan Huafu above 5D2, and it will be enough from beginning to end. When the shutter button is disabled, you will be a master. The mid-range is basically useless, the two sides are not docked, the performance is not good, and it is not cheap.

Pure personal opinion

In your case, I think 5D2 is the most reliable, the price has dropped almost, and the cost performance is high. 5D3 is much more expensive than 2, but its performance is not much worse. No matter how expensive 1D or Freescale Hasselblad is, if you really don't care about money, you can consider it, but the price of 10 to 200,000 is estimated to be beyond the reach of ordinary people.