finasteride's side effects are related to its main effect, which is reducing DHT, which is an androgen. so libido reduction, gynecomastia (sometimes permanent, usually isn't), shit like that. its not actually super common to have problems with it, that usually happens if you're already having endocrine problems or taking other medications that affect your hormone levels, and for most people who do the problems do go away eventually, though they can linger for a while cuz hormones. transfeminine people with hair loss can take it with basically no side effects (me), we don't want androgens anyway.

minoxidil works for some people, but it only works as long as you take it. basically as you lose hair the capillaries that feed blood to your hair follicles shrivel up, and if you topically apply minoxidil to the area of scalp you want more hair on it it dilates those shriveled up blood vessels, artificially increasing blood flow to that region of the scalp and putting the follicles into the growth phase. its technically a hypertension medication, but people figured out that if you put it on your skin it just... makes more hair grow. kinda weird. it doesn't make the hair "grow back" though, at least not permanently. the blood vessels just shrivel up again when you stop using it. it can also cause swelling and other localized blood vessel junk, but every medicine has side effects. if you get it on other parts of your body it will make hair grow there too, and if you use too much then you have a hypertension medication in your bloodstream, which can be not good for your heart. that is also rare.