I like Mossberg shotguns. Good choice.

My first shotgun was a Mossberg 590SP. I initially swapped the stock for a pistol grip...even after reading all the posts about how tough it would be re: recoil and accuracy, and I also read a lot from folks who like the pistol grip setup. Personally I learned to like it. I found it fun to shoot, easy to carry around in my truck, and I practiced shooting with the pistol grip till I was accurate enough to hit what I wanted. Recoil became less of an issue for me as I learned how to do it correctly. After awhile, I realized I really liked my 590SP in its original form, I switched the 590 back to a shorter Hogue stock, and then I purchased a PGO Mossberg 500 Cruiser which I still enjoy shooting to this day. It's my primary HD shotgun.
I don't hunt, so I like the ease of use and portability of the PGO 500 for home defense, but mind you, I have shot a few thousand rounds through it with that grip and I can hit my target. I have also acquired a 6 position tactical stock with pistol grip that I switch out from time to time.
To the OP, since you mentioned you were conscious of cost, I would suggest getting the Mossberg 500 that comes with both a pistol grip and the standard stock in the box. Once you shoot the heck out of it both ways, you'll be able to choose your preference re: stock or pistol grip. Most will certainly discourage the use of the PGO setup. I personally like both....and you won't go wrong with a Mossberg.