i dont know where to begin with this one.

first, if you are relying on your mom to pay your electric bill, then maybe more reptiles isnt a good idea until you get out of school and get your own place.

second, unless you have a huge room with tons of animals and are running a bunch of heaters and fans your bill shouldnt go up much. even if you get more and give your mom 20 bucks a month you should be good

finally, im not too big on multiple kinds of herps but i do know some small lizards, colubrids can be kept at the temps you have said above. but in the summer you may have to cool the room so they dont get too hot.

someone will post soon im sure with more info on different species for you to consider.