The thing to consider is whether you are buying a "two year plane" or a "ten year plane". How long do you intend to own the aircraft? If you sell the plane two years after an overhaul you will raise the resale value by maybe 50% of the overhaul cost. This makes your cost per hour quite high. If you still own (and fly) the plane ten years later, the overhaul will have been a wise move as it is still returning value to you.
I think you are better off buying a generally good aircraft with a mid-time engine. Look past the hours on the engine and look at how many years since the engine was overhauled. An engine that was overhauled 30 years ago will need an overhaul even if there are only a couple of hundred hours on it. If possible find a good plane that has had an engine overhaul in the last six or eight years, has been flown a lot since the overhaul and is well maintained.
Don't sweat damage history as long as it is well documented and properly repaired. Get a good pre-purchase inspection done at the shop of your choosing (I recomend having an annual inspection done without the logbook entry, if you buy the plane take it back to the same shop and have the logbook entry and any necessary repairs done. Explain to the shop what you would like and they will usually have no problem with it.) Pay attention to the empty weight of the aircraft which can vary wildly from one plane to another. Remember every extra pound of empty weight is one less pound of useful load and a C-150 does not have a lot of useful load to spare.
I would say that esa17 has the price right, though you don't really know until you open the engine up; a bum crankshaft can add thousands to the overhaul cost. Figure on a bare minimum of $12,000 up to slightly over $20,000 depending on what you are doing and what comes up. Remember the accessories are part of the cost and the old ones can be mostly good or all junk.
