Vintage cameras are a hobby that has been "dying" for thirty years. It is alive and getting more expensive. The cameras themselves are durable; the supporting infrastructure (film, processing, repair) is the part that has shrunk.
Where to start
A first vintage camera should be fully mechanical and serviceable. The Pentax K1000, Nikon FM, and Olympus OM-1 are the classic recommendations. They will outlast you with basic care.
What matters most
Film cost is the main ongoing expense. A roll of colour negative is around €12, processing another €8, scans another €10. Budget €30 per roll all-in and it stops feeling like a surprise.
What to skip
Repair shops are scarce. A camera that needs a CLA (clean-lubricate-adjust) every 5-7 years is normal. Find a shop you trust before you need them urgently.