Might well be easier to start with a 1.8 20V turbo.
- Already has a turbo, so internals are designed to work with boost
- lots of information regarding it, its a popular engine to tune up
- Will be a mostly standard engine, so replacement parts will be easy to source.
otherwise, you'll end up spending probably similar amounts of cash on modifying yours to work with a turbo, only to end up with (probably) more reliability issues, and harder to source parts for repairs because it's an unconventional engine.
To add a turbo to a non-turbo engine you'll need to lower the compression, possibly uprate other engine internals, get custom ECU software, custom manifolds.... All that custom stuff will cost a lot.