If you want to keep your costs low and deployment simple.
Boot up a linux VM from DigitalOcean (5$ month, 512MB RAM) or Vultr (5$ month 1 GB RAM), Google Cloud (25$, 1.5GB RAM)
Install NodeJS, PM2 , MongoDB (Your DB) and run application using PM (Process Manager : It will restart app on crash, you can run app clusters, a lot more features )
Install Ngix/ Apache and reverse proxy 80 and 443 ports to your Node Js port configured in your config file.
Done !
Few Tips :
Enable GZIP on Ngix/Apache and disable gzipping at node level.