There are a lot on the market (Thermostats that is) There are two basic types on and off and proportional. The difference is that a on off will turn on max power and then off. They are set with a range system a good one will go 1 degree over where you have it set and shut down power and turn it back on once it reaches one degree lower than the set point. (i.e. it will fluctuate if set at 90º between 89-91) A poor one will go 5 or more degrees higher than the set point and 5 or more lower, certainly not great. I'd personally not recommend a zoomed 500R for this exact reason. The better units like ranco and Johnson are borrowed from household duitys and often need to be wired.

Proportional ones flutter (pulse) off and on very quickly and the pad is maintained at a constant temperature if the probe is placed on the UTH the temp of the UTH will be with in 0.5º what you set on the unit.

Personally I always recommend proportional units like the Helix or Herpstat. I feel they cope with changing temps better and are designed and built for what you are planning on using them for.

The disadvantage of proportional units is they cost a bit more around 100$ entry price. On/Off types are less in the 40-70$ range depending.

A T-Stat or some sort of controller (rheostats adjust the amount of power to the heater they work best in a temperature steady <reasonably steady> environment and not so well in an area that changes a lot. Like my drafty old house perhaps your apartment too?) is an essential tool to keep your snake healthy. It is not something you can make do with out.