Cool. This is REAL stock car racing, without the big budgets.
http://www.classicmontecarlos.com/tag/1972-monte-carlo/ and back history.
Monte Carlo’s aren’t family cars per say they’re coupes with ample front room and trunk space.
If you can get one rust free like here in the Carolina region or elsewhere where they don’t use much salt you’re getting a pretty cool car. Especially if you can get an earlier SS with the 4bbl carb set up that should come with the transmission option. We have quite a few early 70’s running around Raleigh NC and they all look great. They’re not particularly hard to work on and plenty of aftermarket stuff to tweak the suspension and plenty of wheel well for various tire sizes.
Gas mileage… I’ve had plenty of 350’s in various vehicles including a 74 MC. I learned a long time ago that if you let he transmission do the work with modest acceleration (like keep your foot out of it) You can get 18-22 mpg A vacuum gauge is also a great tool along with a speedometer. That along with keeping the engine in top tuned condition.
Go for it Man!!
There’s still a few very nice 70-72 Monte Carlos running around here and rust is not as big an issue as it is in other places. The people who lived across the street from my mother in law had a very beautiful one; burnt orange, black interior, and 454 under the hood.
The 73-77 models can hardly be found anymore around here. They all got bought up and entered into the factory stock class at the local dirt track; where almost all of them ended up as scrap metal due to wrecks and rollovers.
The wall at the south end keeps them contained but the high bank and no wall at all on the north end generally meant a cloud of dust and a lengthy, slightly downhill roll.
It’s much more exciting than NASCAR… 
If you have $5k, buy a $4k Miata and put $1k of maintenance in it. It will run forever, not burn much gas and you’ll have the most fun you can have with your clothes on.
You want fun to drive, and the Monte Carlo looks? Try and score a rust free one (if at all possible) for $2500 and add $2500 worth of performance upgrades (Engine, trans [maybe] AND suspension).
@EricJo
Keep in mind the OP is 18 years old. The $1000 he’d have left from the purchase would all go to insurance for most of the year.