I was looking into exactly what you are now a couple of months ago. I was dead set on buying a used airplane to get me from PPL to Com. After talking with a lot of airplane owners, I realized that there was no real way to know if I would break even. An annual could easily run $1k a year, or it could easily be $3k to $5k when you least expect it. I also figure that I will need to spend some time renting a multi engine and doing some hours in a complex aircraft. In the end, it just didn't look as simple as I had hoped it to be. Someone also brought up the fact that I would be doing all my hours in the same airplane and part of the fun in flying is getting to experience different airplanes. One thing I was told was that if I decided to do it, I should buy something common like a 152 or 172 because finding parts and the cost of labor would probably be a bit cheaper.
It all depends on what you want to get out of it.
If you want cheap single to bang out some time in, then turn around and sell it, you probably CAN do better than renting, but you have to keep it VERY simple.
A 172 with steam gauges would be it. No glass, nothing complex, nothing fancy.
Buy it and rack the time up before the fixed costs have a time to pile up, and then sell it.
Back in the day (late 80's). I had the opportunty to buy a Seminole from a local guy. The guy had been leasing the airplane back to the local FBO/School, and they had geared it up...twice (the second right after the first...d'oh!). Anyway, the second time, the FBO's insurance paid to have two new engines, two new props, full paint and the guy threw in a new interior to boot. The airplane had come from the factory with a pretty decent setup (HSI, AP with alt hold, etc...comparatively nice for the time), so this was a pretty bangin' ride, if you discount the gear ups (which really have no effect long term, if repaired correctly). They were selling it for $40k, which was at a fairly steep discout at the time (similar planes would probably fetch $65-70k) The uptick in training for the 90's had JUST started, which would drive prices on 'noles into orbit (eventually the same airplane would fetch $100k+ on the market 4-5 years later), but owner wasn't aware of this.
Gas was cheap ($1.50/gallon), I needed the time, and so I tried to move Heaven and Earth to make that deal happen, and just couldn't pull it off.
My point is keep your ear to the ground...sometimes good deals fall in your lap.
Richman