"Mint" condition, and you intend to shoot the "hell" out of it?
Truly NIB 1917s, ones that have not been arsenal reworked during WW II, are bringing upwards of $1,500.
You can, however, pick up a decent WW II rework, in not so mint condition, for perhaps $500 to $600. If you're lucky, you can get it for less.
There's another, and even cheaper, alternative.
Brazilian Contract 1917s. These were made for Brazil in two separate issues, one prior to WW II, and the second batch delivered after the War.
I got mine for $185. Mechanically it is in very good shape, but the exterior is rough as hell.
One in 85 to 90 percent condition will probably set you back about $350.
The issue grips that come with these guns are, quite frankly, abominations before God and man. I replaced mine with Hogue rubber grips. Certainly not period, but makes it a LOT more pleasant to shoot.
Are they as durable as modern N-frames?
No, but that's the case with any older gun. Metalurgical advances have made new guns more durable than ever. That said, however, your 1917 will be as good as you need it to be for as long as you want it to be.
There were a number of variations on this theme, all chambered in .45, but with differing barrel and sight configurations.
The fixed-sight military version as the Model of 1950 Military, and later continued as the Model 22.
There were two adjustable sight target versions: The Model 1950 Target, and the Model 1955 Target, which were continued as the Models 26 and 25 respectively.
The Model 25 was still being made up to a few years ago, and a stainless steel version may still be made as the 625.
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Beware the man with the S&W .357 Mag.
Chances are he knows how to use it.