I'm on a project that breaks even + some pocket money. Main problems is the code base which needs a major overhaul in order to reduce cost of change & maintenan

I'm on a project that breaks even + some pocket money. Main problems is the code base which needs a major overhaul in order to reduce cost of change & maintenance. I don't see a meaningful way for incremental ( = over a long time) refactoring, because that would increase code complexity for a long time until the incremental refactoring is finished while we'd still need to implement CRs and fix bugs. Any refactoring has to be done in a big-bang approach, but the project isn't generating enough money to fund that downpayment. Edit for motivating factors.