My passenger train services ended up being profitable almost straight away, once I built them. Admittedly, until I got the first decent trams on the scene, the local bus services were barely breaking even, but I took that as a reasonable loss-leader for being feeder networks for the intercity train service.
True, a couple of cargo routes does grease the wheels, and you probably won’t earn enough from local bus services alone to afford your first train service, or even to replace the buses when they become obsolete, but if you plan them well, even the first train services can be a big earner. You do have to be meticulously careful about ever sending the trains into the depot though, as having them out of action for even a few months can cause a financial setback that can take a couple of years to recover from.
I actually found going for the Penny Pincher achievement helped me immensely. You just aren’t in a position to weather much loan-interest early on… even the initial 30k per year stings… taking on any more debt can seal your fate from day one. Waiting until you build up the funds for an expansion is almost always better than being impatient and taking out more loan.