The mosin nagant is not really a rifle for beginners.
The safety is very hard to operate, and many females or very young people will not be able to engage it at all. It requires pulling the entire bolt backwards with a lot of force, and then, while keeping the force constant, rotating the bolt such that a flange engages in a channel.
The cartridge is large - about the equivilent of a 30-06, so it kicks - your picture shows the carbine variant, and because they are short they kick even more. The standard version rifle is a long piece, as was common in the pre WW1 rifles. It takes some practice to hold a four foot long rifle steady. It is deafeningly loud.
With practice, however, it is a great weapon. Ammo is cheap and plentiful, and the heavy ball surplus will blast through wood, masonry, and at close ranges, steel and bulletproof vests. You can outrange an AR type rifle by hundreds of yards. The external magazine has a trap door, so unfired rounds can be dropped out into the open palm without having to cycle the action - a very useful option imo.
The mosin is very easy to maintain, and the bolt assembly can be completely broken down with no tools in a pinch. The action is so robust that it is hard to imagine it jamming seriously. As you said, for $100, it is a bargain. The spike bayonet is wicked. Hunting ammo is now available so it can be used as a deer rifle.
Great guns, but to get the most out of it and master its foibles, spend a fair amount of range time first.