Dragons are very territorial a solitary creatures. One will always dominate and stress the other one to the point of not eating and not getting to bask or get good uvb if kept together. Also the possibility will always exist that they can mame, and/or kill each other. It can happen in an instant and with lethal force. If you cant afford 2 vivs, just get 1 dragon, it will be safer!!! Even keeping them within sight of each other in separate vivs , one will show dominance over the other and, cause stress.
Here is a couple of pics of a dragon that had lived with another one for two years till things went south.