You do not need to buy a whole separate tank for your other snake. In fact, you'd be better off housing him in a nice low sterilite tub. Depending on the size of your snake, which I'm assuming is small, a 12 qt (yes 12) would fit him very nicely.

You put a heat pad like Desert Heat on one half of the tub, and control the temps with a thermostat or rheostat.

You can buy an accurite thermometer/hygrometer from walmart for 12$, they come with a probe that you can put on the hot side to make sure the temps are always around 90 degrees F.

The unit itself should go onto the cool end, and it will measure the air temps and the humidity.

Hot side: 90
Air (ambient): 83
Humidity: 60%

You can give them 1 hide, and put the water bowl on the cool side. You snake will be warm and very comfortable. When you do this, leave him to adjust for a week, and offer him some food.

This same set up will work very well for a sick snake, so no need to go and buy a cumbersome tank that can be hard to control the temps in.