I don’t think the landlord is going to approve you attaching an electric heater, that wasn’t specifically designed for that purpose, to the metal stairs of his building, and I’m pretty sure any city building inspectors will have second thoughts too.
Yep, you’re right. Furthermore, you lose any ability for snow to blow off of its own accord.
Perhaps a better plan would be a duty cycle. Even then, I bet it would use a lot of energy. However, the OP might be interested in looking into something like these roof/gutter de-icers:
They’re 5 to 8 watts per foot. That’s gonna add up! Fortunately there a control system.