Smoke smell should eventually go away...hopefully. I would be more worried about it being an AVIS rental car. Rental cars, especially Mustangs, get seriously beat on...at least in MY experience.
Well I can live with the smoke smell if it never goes away but the car seems mechanically sound. I had to replace the Engine air filter and cabin air filter as well as buy a new set of tires for the rear of the car. Seems Avis sorta used up all the consumables and sold it.
Its a V6 automatic and you cant even do a burnout without a tune so im not sure how much of beating it has taken but it should be fine since its still within the Ford power train warranty and the dealer sold me a WRAP warranty that should cover anything else. Not to mention the dealer warranty's its power train for life. So I have like 3 warranty's so hopefully ill be ok