Take a look at this Propecia DHT inhibition chart.
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Don't take it as gospel truth though. It's specific to each person and case. If you're worried about sides, you have a couple options.
1) Start on a low dose, as you said. 0.25mg may suffice depending on your severity of hairloss. Though if you're losing ground quickly I'd advise at least starting with 0.5mg.
2) Get your hormones tested! Have you done that yet? I saw a study the other day (I think it was posted somewhere on this forum the other day) about there being a correlation between more severe side effects and low testosterone when using finasteride. Don't take this as gospel truth either but there was a study done.
Hormones to test: Test, Free Test, SHBG, LH, FSH, Prolactin, Progesterone, E2, TSH, T3, T4, fT3, fT4, DHT, DHEA-S
Edit: And don't get too hung up on side effects. Despite it seeming like everyone suffers greatly, you're viewing the situation from a warped perspective. Most who get success from these hairloss drugs don't feel the need to frequent forums such as these at all (and rightly so!).