The idea of having a 22 conversion kit is so that you are using the same grip and trigger control. Ideally you would have the same sights on the conversion kit as you would your actual caliber slide assembly, so that everything would be the same, besides the felt recoil.
So buying a junker or a totally different pistol to set up a dedicated 22 cal pistol would be a waste of money and defeat the purpose of having the ability to convert a firearm to 22 cal. If you are looking for a dedicated 22 cal pistol, there are several models on the market for under $300 and will give you great results. Hell my buddy bought a single action 22 cal pistol, made an actual gun belt for it that has 22 cal LR bullets that wrap around the belt. All that just to fulfill his dream of being a cowboy. :doh: I think he has less then $400 in his whole rig and I must admit it is pretty cool.
Now if your looking to fine tune your shooting ability, build your fundamentals to an advanced level and or just get the best bang for your buck. Buy a kit for the gun you shoot with and a few bricks of 22 LR then hit the range.:2c: