A lot of people are sensitive or allergic to scents or perfumes, so you are going to have unhappy customers. 

I wish you luck, I'll cross my fingers, hell I'll even light a candle for you this Sunday.

.”― Carl Sagan, The Demon-Haunted World: Science as a Candle in the Dark

Many things can leave smell or residue (cigarettes, marijuana, vaping, candles, greasy food fry).

Whether it is pot, cigarettes, vaping or even candles; there is damage and odor that can occur.

They lite a candle by that was about it

Small rental properties don't hold a candle to big deals! 

If the unit is well-sealed(you can check for drafts by walking around with a candle and seeing if/when the flame blows(super-cheap way,) or get an energy inspection(more $$)) and insulated(double-pane windows at least, proper wall insulation- and maybe ceiling too?

Some will burn incense, scented candles, or use air fresheners to cover up the odor before you come in.

I know I was frazzled the day they came in with their sales pitch, but point was they were professional - we verbally discussed "staging apps for online photos" and "candles, scents" for showings.Come to find out; all that is for listings that are for sale, not rent.