How do you charge clients for propane?

[Kim Handelman]

Hi All, 

I just bought a duplex. I put my mom in one unit and inherited a tenant in the other. The heat is fueled by propane. One furnace with 2 zones. How do I charge the tenant for the propane? They don't deliver on a regular basis so it's not like I can bill the tenant monthly. Also, the previous landlord didn't get a security deposit and the tenant's lease is up Dec 31. Can I ask for a security deposit starting Jan 1 when he goes month to month? Thanks so much!