You can buy the plane but I would first learn in something a bit less complex. Getting insured for something like a Cherokee Six as a student pilot would be prohibitively expensive if not impossible. I bought a wrecked T-210 and rebuilt it. I had just recently got my high performance sign-off but the insurance just about killed me in cost. And that was in 1980. I am not saying you couldn't learn to fly in it but it might prove to be impossible to solo in it.
It's a big step, that's for sure. I had a student of mine buy a Cherokee Six 300 and we got him his private license in it. His insurance required him to get, I believe, at least 20 hrs of dual instruction before he was covered to solo. Of course, this was back in about 1987. From what I remember, he had a few hours in a C172 before getting the Cherokee, but he progressed at about the same pace as my other students who were flying C152/172's. I'd check carefully with your insurance carrier before making a decision. That and have the airplane thoroughly checked out by a good A&P.
OLD PRO Good Lord! Why not buy a F16! I would rent or buy a Cessna 150, Cherokee 140 ,0r a Cessna 172 to start out with. By the time you get your license you will know what you like. I had a student that started out in Cessna172 and got his instrument rating. He bought a Piper Cherokee six with 300HP. He has invested in glass avionics, GPS's, engine monitors ,and he has more money in it than it's worth. He has had to have engine work(New Cylinders) wing crack repaired, painted,and new lights added. It looks great, but shopping around would of been less costly. These old planes have many AD's (required maintenance) and can really add up at annual. Look at the latest Comanche service bulletins! Get a good and experienced IA to look at your prospective purchase. Costs to note: annuals, insurance,hanger,fuel, AD's and operating cost. Hope this helped