Could a person in America in the 1970's support themselves, pay for?
Yes. I did it working part time as a supermarket checker. Of course, I had an old junky car, no computer or cell phone, a tiny b+w TV, a room mate in a 1 bedroom apartment in the worst part of townbut my part time job came with good health insurance. Got clothes at the thrift store, slept on a 2nd hand mattress on the floor. My only luxury was owning a cat, who showed up at my door one day and demanded to be let in and fed.