It'd work so long as what you're plugging in are exactly the same, like heat tape that's the same length, and setup exactly the same on duplicate cages.
If the temp in the room is relatively stable, a simple rheostat if you monitor the temp would be a cheap solution until you can get something like that hydrofarm taylor linked earlier. Light dimmers from home improvement stores are only like 10$. Not perfect but far better than an uncontrolled uth.