You an RP in this area if you've had your RP profile stamped by a moderator. You do not need an official cert/art!

However, you cannot RP in Doors, or find the place, until you have received art through a flatsale, raffle, auction, contest, etc. Your character should have absolutely no knowledge of the supernatural world, no clue that magic exists, should be 100% human/normal. However, they'll be able to theoretically learn of the supernatural through RP -- by interacting with supernatural characters.

In addition, the RP you do before getting art does not count toward RP requirements to grow. That'd just be silly.