Your facial hair won't really be impacted by HRT at all.
And from experience, I'd recommend starting facial hair removal ASAP. Not only the sooner the better, but if you start before HRT, you'll generally have much more of a tolerance to the pain and can therefore go quicker ( and so it will cost less ). But yeah, it's pretty expensive.
For other body hair, YMMV... You'll have to wait and see... or try laser / electrolysis.