Free: Contests & Raffles.
I wouldn't over-think it. Just about any shotgun will kill a turkey.
as light a shotgun as you can find... if you sit in a blind nevermind.. but if you walk that should direct your decision... tss will cover performance for whatever gauge you choose... 410/28/20 would be all i looked at.
I took my first turkey at 45yards with a Mossberg 500 20GA youth model. It's light, cheap, and reliable. Invest in a decent choke and pair it with a good patterning round and you are set. I did end up adding a pad to increase the LOP, but I still grouse hunt with it every fall almost 20 later.
What about sights? Okie John