Is there a requirement to hold my licence for a certain period of time or not if i'm renting from Denver Int Airport?

Not exact sure what you mean . We don't hold licenses, we just verify you have one and write down the number on the agreement.

Some companies require you to hold your drivers license for a minimum of 12 months before you can rent a car, is this a requirement for enterprise as well or not?

You need your license to drive, so no...