Medic is the one role where levelling and earning are the same action. Play it inside the hotzone beside the biggest friendly crowd you can find: revives there paid $1,600 [BETA] against $400 [BETA] in the open. Solo or duo, medic income collapses.
Kit: the free Emergency Resuscitator (one per life, cuts a roughly 30 second revive to 4-5 seconds), bandages, and an SMG so your kills feed Medic too. The PP-19 at Medic 4 is the early power spike.
Bandage teammates, never yourself: self-aid pays $0 [BETA] and no XP. Before reviving someone, check their inventory and use their own resuscitator on them.
The milestone is the Defibrillator at Medic 11: $50,000 [S1] to unlock, $1,600 [S1] per buy. It revives instantly at 35 HP instead of 10 and paid $2,400 [BETA] per revive in the hotzone. Buy it the moment you can afford it.