As others have mentioned, it depends on where is your targeted region.
Caracao license is the easiest you can get as far as my knowledge, basically as long as you pay for their fees you can get a license from them, there's not much of regulatory.
But if you want to operate in countries like UK and some other EU countries, you will be required to obtain a license from local agency like UKGC.
It will be harder to get one because they will really look into your operation practice, like AML and gambling responsibility measure etc.
And you could easily lose your license if you're not operating in their guideline.

And yes, technically you can "rent" a license from someone who is already registered.
Basically you will be "sharing" the license, so both of his and your websites are operating under the same license.
The problem is, if he or you violate the license regulatory, both of you will be punished.

So I'd say, if you're intending to get a license in Caracao, then just get one for yourself.
Because it's easier to get and there will be less problem.
If you're intending to get a license from agencies that have tighter regulatory, then you can consider to rent the license from someone else.
Just make sure both of you are operating within the guideline.