So, a couple points on this:
- Any VPS provider you choose should provide a recent enough system image to allow you to readily install and setup an OpenVPN server. There are a number of scripts on GitHub that automate that process across all common distributions and which should work on any random VPS. The second one I linked has an affiliate link on its README.md for a provider that offers memory restricted, disk restricted, but relatively bandwidth heavy instances (probably sufficient for a single-user VPN server, definitely not for anything more complex) for $1.25-2.5 a month. You can find a lot of offers like this if you look around.
- What do you see the 'private VPN' being useful for?
- If for privacy, this is questionable.. rather than having your traffic from client devices come from whatever home and work and public networks you connect to, everything will come from one IP, which is a step back.
- If you want to dodge IP bans on chan sites etc, just bear in mind that many of these may apply access controls to traffic from known datacenter IP ranges.
- If you want to get around a China-level protective firewall, it is better to camouflage your traffic more by using something that looks more like regular HTTPS traffic. Use something like ShadowSocks. There are easy install scripts to set that up too.
Now.. if you mainly want the seedbox, maybe research your options for what will get you the best seedbox solution, and then if you can easily do the VPN too and it's going to allow you to do something actually useful, then that's a bonus. Or, go with a regular VPN offering that's going to allow you to download torrents and mix in your traffic with others some.