Buying an Ercoupe

Depends on price, condition, and what you're willing to deal with. If the center spar is good, then turn your attention to the engine. Having sat unused for all those years, there is a possibility that corrosion has set in. While it may run great and have good compression, you don't don't what the cam lobes look like or the lifters. If a reliable mechanic can get a scope in there and attest to their health, then it's worth considering. The big issue nowadays is that a rebuild costs as much or more than the airplane is worth! Ideally you should change the oil, fly it for 30 hours, then have it looked at and an oil analysis done. Hard to do when you're looking at someone else's airplane! But if you can satisfy yourself that the engine and center spar are healthy, everything else is pretty manageable.