My 951 recently burnt, causing a frantic search to get back to a 911. Fortunately, I LUCKED out. Within several weeks mine came up on craigslist. I was looking for a 3.2 liter g50 and all that stuff, but ended up with a 78 sc that drove nicer, was in better shape, had lighter steering, and reminded me of an earlier 911 I drove. It brought an instant smile to my face, while the others (3.2's-some costing much more) that I drove did not. Could I have gotten a better deal? Maybe. Did I want a car this old? No. Perhaps I could have "pushed my luck", and kept fishing, but I would be still searching over six months later. I have kept an eye on the market and little has shown up locally since then. I needed my fix and I needed it quick.
Many people say 6mo- year or longer. Some people enjoy that. For me (with a small kid), it was stressful. Particularily the thought of travelling regionally just to make test drives, so I jumped on my car, and I'm smiling every day!
I also suggest learning as much as you possibly can about all these cars
while searching, keeping an open mind, and being open to possibilities. All of these cars will need maintenance. All will have quirks. It is a journey. Good luck!