Have you looked after fish before?
If not i'd maybe advise against getting discus, they aren't the easiest fish to look after
Main reason for this is that, discus love really clean water, and they need really clean water to grow properly, i've heard of people changing water daily for them. This leads to debate about whether or not to use gravel (it's easier to keep water clean without gravel)
If you do decide to get them, make sure you get a minimum of 6, because they are schooling fish.