mustang lx 5.0l smokes when revved

[connella08]

i am looking at buying a real cheap stang thats down my street. its 500 bucks, has 3 small rust spots. else looks fine. when its revved, smoke comes out of the exhast pipe. is this due to bad rings allowing oil to seap through. it wasnt started since december and when it was first started, it smoked quite a bit and ran a little shakey. the smoke cleared, but still runs a bit shakey. also, i noticed that when it chakes, the oil pressure goes down a bit then jumps back up. it is however low on oil to begin with, but that brings me back to the smoking. btw, is smokes out of the mufflers, not the engine. low oil due to bad piston rings? please, get me some feedback asap. i need to convince my dad its a good deal for 500 bucks. it has 136k miles on it, but for 500, thats not that bad. as long as the smoking issue is resolved.