These are the guides I used; pretty simple to follow. You can use the $5/month AWS option (500 MB RAM), but you need to add a 1GB swapfile for more memory.

https://www.accrubit.com/how-to-easily-setup-tierion-node.html

https://www.digitalocean.com/community/tutorials/how-to-add-swap-space-on-ubuntu-16-04