Veg near, but outside, your primary flowering tent and / or grow and flower autoflowers outside your primary flowering tent.
Any electricity used in the form of a light can be dual purpose, creates heat and supplies light. Use thermometers that record 24 hour hi/low temps and become familiar with your grow room temps both inside and outside your tent when it's cold outside so you'll know when or if you need to add supplemental heat, which of course can be another light.
Fluorescent 4 foot lights are cheap if you're on a budget. Good luck.