Conclusion for iCloud Check & iCloud Locked devices
When it comes to buying second hand Apple devices the iCloud Check service will help you to identify if they are iCloud Locked or not.
You should avoid purchasing iCloud Locked iPhones at any cost since you will not be able to use them properly (And in some cases they can be unusable).
If you are in the unpleasant position to already bought an iCloud Locked iPhone, there are solutions, but they cost.
For iCloud Locked iPhones with “CLEAN” status, you can purchase an iCloud IMEI Unlock service as long as your iDevice is eligible
For iCloud Locked iPhones with “LOST” status, you can get iCloud Bypass 2020.
For iCloud Locked iPhones with “ERASED” status, there is nothing you can do. You can only sell them for spare parts and cover some of your expenses.