Honest appraisal to follow as this is an appraisal forum. Cover your screen.
Bottom end with condition issues. If you have the time/tools/aptitude/workshop and access to free parts, OK. When I get bikes like this (and I do) I take them straight to the co-op. I really can't touch a bike like one of these without losing money. There are better projects out there so I save my time for those. It takes the same amount of time, and the same $$ in parts, to rehab a bottom end bike as it does a mid level bike.
Of course, its not all about making or losing money. But on personal projects, I aim higher as better stuff is out there at low prices (I look a lot). My favorite bike I picked up for $15 at a garage sale. It had definite condition issues, but underneath was a top of the line model. I have upgraded it many times over the years. A good bike does not always mean an expensive bike price wise.
The co-op can use volunteer mechanics and donated parts and get these ready to ride. Since I don't have free volunteer mechanics (other than me) and free donated parts, it doesn't work out so well for me. I run out of time before I run out of projects, so I prioritize the good stuff first. I am an avid garage sale person, so I am always looking. I'll buy the bottom end stuff and drop it off at the co-op on the way home.
Hi ten steel frame, nutted rear axles, claw RD hanger, stamped drop outs, steel chain rings, steel handlebars, seat post, rims, hubs, etc.
Realize back in the day brands felt obliged to make low end bikes. For every good bike, brands made hundreds of really low end stuff. Nothing against Shogun, I bought two Shoguns last week and have owned many more.
Randy's mytenspeeds website is a great place to learn what makes a good vintage bikes.
http://www.mytenspeeds.com/My_TenSpeeds_1/