1) how much does it cost to start?
2)how much profit I'll be able to take out from mining?
3)The best way to start mining?
1) how much does it cost to start?
For the sake of experimental or a hobby, If you have an existing Personal computer or an idled pc units, you can start mining without any cost except for your power electricity, but it doesn't mean you can do profit from it, it could be a waste of time depending on your hardware.
2)how much profit I'll be able to take out from mining?
that's will always depend on many factors like, Hardware, Coins you are mining, Power rates
3)The best way to start mining?
Just do my answer for your number 1 question.
:-)