What is the cheapest pet to buy that is easy to take care of?

A pet rock. None of the live ones are cheap !!!

Invertebrates are the cheapest. Tarantulas, scorpions, millipedes, roaches, praying mantids etc. Very cheap, very easy to care for and very low maintenance.

I personally think that the easiest pets to take care of are pet rocks. first of all you really don t have to feed them anything and maintenance is very low other then a occasional walk. they are good around children but sometimes get a little frisky and jump out on to the ground below them ending up on children s feet on sadly their heads. other then that I would say pet rocks are the way to go.

Hermit crab or stuffed animal.

If you have a decent sized tank (3+ gallons), a heater, and properly clean the tank...bettas are very easy. They're tough, so even if something happened on accident, they should be good.
I don't agree with the snake ideas. I have one and they do take a little work. You have to have a big tank, know when they're hungry which can be difficult to determine at times and keep the tank the right temperature all the time. I love them, but I don't consider them easy or a beginner pet.
Hermit crabs are a great choice too. Very little work to owning them. Just make sure they come from a good place, most people that sell them (like the places in tourist towns) will sell you a sick or very old crab and they'll die crazy soon.

Pet rock. Chia pet.

Fish are very difficult to properly care for, and most people that say they are easy end up murdering the fish pets before they are even adult animals! For example, most people kill their goldfish in the first two years, before the fish is even considered adult or able to breed. A goldfish should live close to 40 years!

Small snakes are not bad pets. They are quiet, do not require a tank full of water or weekly water changes (like fish), stay small, and do not eat daily. A corn snake or similar relatively small snake is a good pet if you like easy. Land hermit crab are also relatively easy, and of course triops, seamonkeys, etc are choices.

fish or lizards/snakes possibly?

Fish are hands down the easiest pet to take care of.

goldfish

A fish is usually the safest option for a first time pet owner. It will get you into how a pet should be treated and all the necessities they need. They are usually fairly cheap and are very easy to take care of - if you feed them and change the tank water.

betta fish