It depends a lot on the esport in question, at the moment teams in VCT are fine, because riot pays an insane amount to each team. This isn't even including bundle sales that boost revenue significantly. Anything outside of VCT will be tough due to the lack of viewership and tournaments.
The revenue model differs between esports, for example in CS the circuit is much more open and the revenue from in game items is absolutely massive. There's smaller orgs that managed to keep their rosters running for an extra year or even two just from the money generated by getting to the Major.
Outside of making big events, there's also the revenue model of being a "feeder" org. You basically find the next talents and get them to the tier 1 level, then you can sell their contract off for significant sums, there's an org in CS that in the past has reported higher revenue than most tier 1 teams just by doing that.