Two-layer boards are now absurdly cheap, even in small quantities. The boards available from DirtyPCBs or Elecrow are perfectly satisfactory for most hobby projects. Four-layer boards with ENIG and fine pitch are now well within the realms of affordability, particularly small boards from OSHPark.

The most economical stencils are avaliable from OSH Stencils. They offer mylar stencils for $0.64/square inch, with a minimum charge of $5. Mylar stencils are perfectly satisfactory for prototyping or even short production runs.

https://www.oshstencils.com/