We thought of having a VAS server at home and collected everything every bit of hardware but the problem we found is that how to get a subnet at cheaper price like that of digital ocean or any other server, how do they actually get IPs?
The answer is the same world over. You have to purchase a network connection from a telco that is willing to supply a subnet of IP addresses or a single IP address. Most are not willing to supply more than one IP address without a commercial connection with an SLA (service level agreement) and a hefty price tag. Otherwise, many broadband providers will provide a single IP address for a moderate price over the standard subscriber fee. You should be able to host almost anything you want behind a single IP address giving that your firewall or proxy will allow it. Generally, these cost more.
Not sure, but if it can be used with hostnames instead of IPs, you could use http://www.noip.com/ to get a free Dynamic DNS address, and install the client on your network so that the hostname always has your current IP address.
That way, even with a dynamic IP address, you could always reach it by hostname.