@julian Were I needing to minimize costs as much as possible, I would be considering repurposing a retired PC running Unix/Linux (whatever whomever is going to undertake this endeavor favors), set up DynamicDNS, and then route everything to that PC. Maybe put an OpenBSD packet filtering router ahead of everything to keep packets sorted. Toss an inexpensive but high VA UPS into the mix....
Zero additional costs since piggybacking on existing internet connection. Presume low traffic/development box. Once you need more, you will hopefully be able to afford a virtual machine from your preferred provider.
My shootin' from the hip $0.02. You get what you pay for. Caveat emptor. 🐕 🌴