First time getting snake!! temp question please help me

[gusanr14]

Hello BP people!
I just got into the forum today, and I am still doing research about ball pythons!
I have learned like basics and set ups about snakes.
Here is my plan, I am going to get a plastic tub, different sizes for when they are small and grown up. For now, small one of course. I will get a hide box and water dish with probably newspaper or paper towel bedding. Humidity wise, water bowl seems to be fine in my room, maybe misting time to time to have enough humidity. My question comes to temperature.
I know that hot side of the tub should be around 90 degrees and cooler side around 80 degrees. I am going to get a heat pad with thermostat so hot side don't seem to be a problem. However, I was wondering how to control the cooler side of the tub. It should be around 80 degrees, and my room temperature stays around 75 maybe higher during hot summer and during cold days winter, it drops to around 70~73. One way I know is to raise the room temperature with space heater but I can't use that all the time when I am not around because I will be always worrying about house burning in fire and high electricity bill. I do respect animals but just for one snake, I don't think I can manage to turn on space heater all day long. I see all these guides about how to heat the hot side but no information about what to do for cooler side since temperature for cooler side shouldn't actually be cool. My thought was that, if heat pad heats the hot side, heat will rise and since it is a plastic tub with lid, tub will store heat very well and eventually heat the ambient temperature since it is not a high tub. And I thought maybe those heat will go around the entire tub and heat enough for the cooler side. I mean thinking logically, heat should be going around the tub if it is heated right? maybe Im wrong. Also could try the blanket method. Another heat pad or source would not be one of my choice due to many reasons. Any suggestions from BP owners? Some of the breeder told me that the heat pad will just do fine like what I thought but I just wanted some opinions or suggestions from you guys. I will be testing out everything before I get a snake so don't worry! haha if nothing works out, I might go with corn snakes, but I want ball python!!!!! help!! lol
Thank you!!