I just got an M&P as well (full sized 40). Love the gun. Anyways, why do you intend on getting a holster specifically for the range to fit a gun that you will 99% carry otherwise? I understand IWB holsters can be uncomfortable with hot guns, but I personally see the range as an opportunity to train myself with the gun+holster combo, not just for putting holes in paper. I would recommend only getting holsters for that gun that you will actually use AND practice with. Drawing from a holster is tricky to do safely and effectively and can be dangerous to do without adequate practice.
Why have you chosen IWB? Is it for deep concealment or do you think you can't hide your gun(s) in an OWB holster? For the longest time I believed I could only carry my full sized XD in an IWB holster. I ended up eventually making my own holsters, and found that a properly designed (for the gun AND individual) OWB holster can easily hide a full sized pistol with proper clothing. I live in Alabama, and all I wear other the gun is a Hawaiian style button-up shirt or sometimes even a T-shirt. Hiding a compact only gets easier.
When looking for an OWB holster, you need to see how high the gun rides on your waist. Since you carry a compact, it's not as critical, but you still need to make sure the barrel will not sink below the hem of your shirt. Try looking at belt loop / belt slot attaching holsters. You will want one that pulls the gun into your side, but doesn't bury the grip into your waist either. The paddle holsters you see in stores don't cut it, and aren't really meant for concealment. They add space between the grip and your body, which is great for drawing outside of concealment, but is next to impossible for many people to even remotely conceal.
The $50 criteria is the next hurdle. I take it this is your first gun and also your first holsters. Why spend $700+ on a firearm (I include break-in ammo in that price) just to go cheap on your holster. Would you buy used tires for a sports-car? 99% of the time you will be using the holster, not the gun. Only while at the range or in the extremely rare defensive scenario will you actually be using (aiming) the gun. That being said, $50 can be doable for a simple OWB holster, but you're going to have to do some shopping around to find a good one.
As I mentioned, I am a new holster maker, and can help you out if you can't find one that you're happy with in stores, but I would still shop around locally to see if there is one in a store that you like and can use.