Good morning to you.
Do you want to rent a VPS just to run Pi-hole ?
Why not setup openVPN on the Pi @ home and have your mobile devices dial in.
Is allot cheaper.
If you rent a VPS to run Pi-hole, you'll need to setup openVPN anyway as you cant run an open resolver (not recommended).
Have a read at below link bout those open resolvers and how they are used for attacks etc.