If you have had a budgie for a while and you want to get a new one is it safe to keep them in the same cage?

Well it is sometimes. If you want to put a budgie with another budgie, you have to put the new budgie in a separate cage first. Then place the two cages next to each other so that the two budgies can get used to each other. After a few weeks, a month is best, you can put the budgie with the other one. Leave them together for a few days. If they attack each other, it is best to separate them again.