I'm not a "flipper" but I agree it is not worth it. The rusty chain and likely need to replace the freewheel, the nasty dirt emerging from the BB and the almost 100% likelihood of needing to replace rear brake and front derailleur cables and housing is going to add up very fast to more than you would pay for a rideable project bike. Learning on a bike that will likely be full of frustrating and unexpected problems is not a good idea. Best to learn basic adjustment and maintenance first.