When you become a step-parent do you expect to take on the role of "parent"...?

I think every case is different, I know you're a single mom, so that's probably why you worry about this stuff, but I think you should evaluate every situation separately, there's no good or wrong pattern to follow, and all kids will see you differently. I believe it depends on how open the kid is, how much he lets you in and ultimately, if he/she wants you to take on that role. Also, sometimes you just grow to love the kid that you don't even notice when you started acting like a parent, I'd just let things flow.