I want to put slicks on my bike since lately I've been using it more as a commuter. I will occasionally hit the trails(on the weekends) and I've decided that instead of swapping out tires once a week, I'd rather have a pair of extra wheels, which would make it much easier for me.

I have an entry-level bike, which is fine for my uses, but I need some help on what kind and where to buy a decent wheelset that doesn't cost more than my bike did. Is there a decent wheelset that can be had for less than $100? I don't need anything spectacular, as the wheelset I have now, is nothing spectacular and works just fine for me. I just need something that is durable and affordable.

Does anyone have any ideas?

What kind of brakes does your bike have?

If discs, swapping out is usually not a problem since the rotor location is standardized.

If linear pull (rim) brakes, there can be a problem with the brake pads aligning with the rim from one wheel to the other. In your case, it may be worth your while to try and get the identical wheels as supplied with your bike.

Following on kenhill3's suggestion and your requirement not to spend more than your bike cost, just go buy a second identical bike and have your wheels to swap out plus a full set of spare parts when you need them.