If we look at why we use candles there are two primary reasons that immediately spring to mind. The first is that we use the flame for focus and meditation to sharpen the nature of our intent. The second is that we use the smoke of the candle to carry the intent of our spell into the world. (I like to speak my spells directly into the flame so the smoke carries my actual words into the air.)
The main spell association with candles is the second example and this is what I'm going to focus on here. (The meditative element can be substituted with music, essential oils or even crystals).
So in order to replace candles in magic we need to find other ways of actualising our intent. Incense sticks would be an excellent substitution but I'm guessing if your landlord has a problem with candles he won't be keen on any naked flames and if he's got smoke alarms installed nothing will kill your spell work faster than waiting for your alarm to start beeping.
What you need is an alternative way to get your intent out there. Having discarded the element of fire let's have a look at how you could utilise the other elements to the same effect.
My first suggestion would be cord magic. I say cord but to be honest a cheap spool of cotton is your best bet. This is ideal for spells when you are trying to relieve yourself of something or to cast something from you. Simply visualise what you wish to leave you while focusing on tying a knot in the cotton. Anoint with appropriate oils and herbs if required and toss out to the winds to allow your intent to drift in the breeze.
For spells of either a protection or a banishing nature I don't think you can go far wrong with using the power of the earth. The traditional spell of creating a witch bottle to represent yourself and draw malignity away from you involves burying the bottle in the earth. Many spirit banishing rituals involve trapping the spirit and returning in (both physically and figuratively) to the earth. If you're using the earth in the same way you would smoke - as a carrier for your intent - bury your spell in something biodegradable that will rot away and let the earth absorb your spell. Burying your intent in a glass jar might not have the desired effect...
Finally there is the element of water. What do you have (or I fervently hope you have) in your home that allows you to flush water from your home back into open waters? Exactly! Any witch worth her salt is aware of the potential of the toilet. Write your intent on toilet paper and flush it. Yes it might not feel as glamorous as whispering into a lighted flame but the principle is much the same and your landlord certainly won't object to it! In a similar vein using water you could use the steam of the kettle to carry your intent into the air - and if you bought a small cheap kettle you could add essential oils to evaporate with the steam into the air. A practical and safe alternative to the smoke of a candle.