Dude i agree with whats been said here already. At 21, you likely have a lot more room to make some significant gains naturally. The only reason Im posting on this is because i am a big fan of var despite the negative opinions of it. Also, I empathize with where you are as a beginner...
You likely was turned on to a video or some info that told you that steroids "arent bad" and "people dont die from using them" etc. and decided to do a little research and found that anavar was the "safest steroid" and made up in your mind to try a low dose.
Fair enough...but let me tell you my perpesctive, since you will likely go out and run a cycle inspite of what others are saying here..
20mg of Avavar will help you hold on to a bit of muscle while cutting, if you run it 6 weeks or more. (which you may be asking for trouble if you run it longer than 6 weeks). And you better make sure your diet is perfect. Either way, dont expect any sort of miracle from this! At best, you may have some decent pumps in the gym & you may be slightly harder during the cycle.
In the times i have done Anvar, ive found no need for PCT. But, this is just my experience. Always be prepared to run PCT after a cycle!!!
Best advice...be patient and wait a while before running a cycle. I know you are probably anxious about this, but everyone here can tell you, steroids are not miracle drugs! You still have to train very hard and eat right!!! Since you have to this anyway, save your money and spend it on some good food & a few suppliments and in 8 weeks or more you can have the same results as you would with running 20mg of Anavar.