What are you trying to build which will take $100 per month? If you go for AWS lightsail, DigitalOcean, Linode etc. it will be about $5 for a small VPS where you can install your own database. Once you feel soneone is going to pay for your app you can upgrade to a bigger server.
If you have a serious idea you can apply for azure startup founders hub which will give you $1000 free credit for a year. AWS has similar programs for startup.
What are you trying to build which will take $100 per month? If you go for AWS lightsail, DigitalOcean, Linode etc. it will be about $5 for a small VPS where you can install your own database. Once you feel soneone is going to pay for your app you can upgrade to a bigger server. If you have a serious idea you can apply for azure startup founders hub which will give you $1000 free credit for a year. AWS has similar programs for startup.