That boat is at a very good price point, but a bad engine can kill any economies. And even Lehman's can have problems. So do a mini survey while you are onboard.
The engine should start right up with only a few seconds of cranking. After it starts a bit of white smoke is ok but should settle down after it warms up. A big cloud of smoke after an extended cranking period is a pretty good indicator of a worn engine.
Check fluids before and after running. Check for water in oil and oil in coolant.
If you go out on the water, run the engine up to wot and watch temp gauge for overheating. WOT rpm should be at least 2,400.
Those are the basics and should give you some confidence that you have a good engine if they all check out ok.