Thirty thousand in 1969 money is $224,472.41 today (inflation rate of 648%). You cannot buy anything on UWS or much of Manhattan today for so little money.
Rex Reed was incredibly lucky and also benefited from kindness of both strangers and friends in landing his Dakota apartment. From above linked NYT piece that has been posted in other threads about Dakota apartments.
"“I moved into this apartment with an A.&P. shopping cart, some books and whatever I could drag over from my little walk-up on 73rd Street,” Mr. Reed said. His only furniture was a corduroy Queen Anne chair and a sleeping bag. The night he moved in, the film star Robert Ryan, who was president of the Dakota’s board, rang the doorbell to welcome him, and the two shared instant coffee, Mr. Reed on the sleeping bag, Mr. Ryan in the chair. “Do you think that happens today?” he asked."
No self-respecting co-op today in Manhattan and likely NYC as whole would allow anyone to buy with just pretty much just what they paid for unit. You have to show substantial assets that prove you can pay bills on time and won't likely be eating rice and beans for years because you've put everything into buying apartment.
Keep in mind however great the Dakota was then and is today the UWS in 1960's and 1970's was just a totally different place, and this included Central Park West.
Rex Reed's apartment wasn't the only one that went cheaply.....
"In 1961, the Dakota went from rentals to co-ops. But two of the building’s most popular long-time residents, Henry and Winifred Blanchard, couldn’t afford to buy their fifth-floor spread and were to be evicted. According to Birmingham, each Christmas, carolers in the courtyard would decamp to the Blanchards for “hot buttered rum, cookies and sandwiches.” Neighbor John de Cuevas, whose grandfather was oil baron John D. Rockefeller Sr., agreed to buy the Blanchards’ apartment for $26,250 and allow the couple to stay on.
After Henry’s death, Winifred continued to live there until her death in 1988. “There was no agenda other than generosity. He didn’t do it as an investment,” says de Cuevas’ broker, John Burger of real estate firm Brown Harris Stevens. Still, the good-Samaritan gesture paid off two years later when de Cuevas sold the place for $1.3 million."