Yeah oil networks like these are a good way to make money early even on Hard, but only if the map allows. Sometimes it's hard to create such an efficient oil setup due to factory placements and gradients.

What I'm experimenting with at the moment for early game trains is inter-town goods shipping. If you can set up unique local truck-based industries in two towns that can be connected by rail, you can easily start shipping goods between them for solid profits each way. For example, if you have a town with a quarry and a construction materials plant, and another town with a farm and food processing, both outputs of these industries fit inside a goods wagon. So running a train between them that moves excess food from one, and excess construction materials from the other, is an easy start-up in many cases. On top of that, you can use that same rail to start running passenger trains a bit later.

Doing it that way around means that by the time your passenger trains start operating when your two towns already have 2 demands filled, making them much more popular for passengers.