2 family house one thermostat

[Jay Durant]

Hello I need help I was owner-occupied 2 family house for 15 years now moving and want to rent my old apartment.  apartment # 2 pays their own cooking gas I always covered the heat and hot water being that I controlled the thermostat one gas boiler, seperate gas and electric meters. Now that I'm moving do I include heating cost in the rent or what? Any suggestions are greatly appreciated. Thanks.