Well, I don’t know how fun a 70s Monte will be to drive. It’s a big old boat of a car that will probably get about 15 MPG if you’re lucky. Despite the V8, it’s also slow compared to relatively modern cars. If it’s a 72, it shouldn’t be too encumbered with pollution controls. I would avoid anything newer than that. Try to find one with disc brakes if you can. If you live anywhere it snows, it will take some getting used to a rear-wheel drive car in the snow, and it will rust like crazy. Door hinges were a weak point with some GM cars of that era too–the doors sag. It has no air bags, but will probably win in just about any collision. It will require more frequent maintenance than something newer. You may have to learn to adjust the points, and become acquainted with the quirks of a carbureted vehicle in cold weather. (and hot) Anyone with a minimum of tools can steal it in a few minutes. If you need air conditioning, you will need to convert it to R134a or pay a fortune to get it charged with R12.
Having said the negative things, a 70s Monte Carlo will be a head turner, especially for younger folks that didn’t grow up driving cars like this. It should be reasonably reliable. The power train is durable and smooth. Chevy 350 motors are nearly bulletproof as long as you don’t run them out of oil or overheat them too much. Maintenance should be easy, and there’s a ton of room under the hood to reach anything. You won’t have to worry about 100 vacuum lines or a catalytic converter. There are countless performance mods for cars of this era and power train, if you lean that way. You can practically live in the back seat. The A/C is cold enough for a walk-in freezer (when it works) on GM cars of this era.
Good luck and let us know what you do.