If you can’t afford the $7-$10K for an automatic failover Generac system look into a self installed transfer switch and a regular 5-8K watt gas generator. The transfer switch isn’t difficult to install yourself but if you are worried an electrician can do it for you. 8K likely won’t be enough to power your whole house but should be enough to power the furnace fan, a few lights and the fridge. Total costs should be in the $2K -$4K range.