Temporary heat using gas

I've got a 1901 two story Victorian that I'm starting to remodel and upgrade to modern things like new electrical, bathrooms, kitchen, etc. , but living here in an area of calif where the mornings are 30 and my home has an old gas floor furnace (which I do not trust), and is currently disconnected, I'm trying to find a temporary solution for heating. Electricity here is expensive and gas is cheap. These old lathe plaster walls seem to keep cold air in during winter and hot air in during the summer.

By spring I should be done with major work and will be putting in a high velocity mini duct system throughout the home.