Yep. It could be used, the most common dosage seems to be 5mg (around $1 per dose).
Finasteride does not seem to be the most recommended AA in feminizing hormone therapy, The AAs that you see mentioned more often are Cyproterone (Androcur) and Spironolactone (Aldactone). However, the one that is coming really strong is Bicatulamide but it is still expensive, $1.50 for a 50mg dose. Spiro (50mg-100 mg) or Androcur (6.25 mg-12.5 mg) cost between $0.25 and $0.50.
Please check Jannet Duff's post on Finasteride dated 16-12-2018, 08:02 PM. There is some interesting info on Finasteride side effects (but they all do anyway).
Hope this will help.