My Ford Transit headlights turn on in off position and turn off in the on position?

I'm a new driver, just passed my test. My van has some issue with the lights: namely, the lights turn off in the on position when the dash lights come on, and turn on when they are supposed to be off. This means that I'm driving at night without dash lights as I need to have the lights switched off in order for my headlights to be on.

Might this be an electrical issue? Would anybody be able to give me advice and possibly know how much this costs to repair?

The switch is likely bad. See a mechanic to get a proper diagnosis. An hour or two for labor (around $70 an hour) plus the cost of parts.

A Mexican Headlight Switch I'd bet. Ford make a lot of their parts there. A headlight switch is a simple switch. Power comes in and its' job is to switch the power to various circuits. The first click should power up the park and tail lights, also dash lights. The second click should power those circuits plus the headlights. Knowing that, your switch is not working correctly and needs to be replaced.

When the lights are off the daytime running light system turns the dash light ON.
When the headlights are turned on th dash lights go through the circuit with the rheostat that adjusts the dash light brightness.
Have you turned the rheostat to full brightness yet? Perhaps the rheostat is turned off!