VPS for a NodeJS and mobile applications?

My question is not code related. But please don't close it. I am posting it on here because I was unable to find a satisfactory answer.

Question: I am hoping to buy an unmanaged VPS from either DigitalOcean or A2Hosting. It will run MongoDB NoSQL server and a NodeJS server. There will be around 10 users who will use the NodeJS web application and will be around 3000 users who will use the mobile apps (Android & iOS). I am hoping to get the $5 plan since there won't be many mobile users from the beginning. Is this a good idea? If the $5 plan wouldn't be enough, which one should I choose?