You'll find diverse opinions on Crescent because they made a full range of models form entry level up to professional racers and because like many boom era manufacturers, they suffered quality laspes trying to meet demand. They were also producing bicycles in South America, as well as Sweden during the boom.
The bicycle in question appears to be an early 1970s, entry level, Sports or Sports Racer model by virtue of the steel crankset and downtube shifters. These models were spec'd with Huret Allvit shifters or Simplex Prestige derailleurs. Yes, it's going to be heavy, about 28-30 lbs but if it's in good condition and fits, $40 is a good price. As a bonus it, has fenders, and it looks like they may be Bluemels. It also appears to have a leather saddle and possibly aluminum rims. I would definitely be paying a visit to examine this bicycle more closely.