if you have to ask questions like that on a forum,I suggest you do not start with mining
it has too many things you have to take into account and a total newbie would not be able to achieve ROI or profit
well to answer your questions:
1.take electricity price into account,it is very difficult to profit with electricity costs over 0.05-0.07 $ for kwH
your ROI could be 12 months or more and by that time faster,more advanced miners could appear and delay your ROI even more
2.buy the most efficient equipment (at the moment it is s9 Antminer)
3. make sure your operations are safe - i.e. you do not run a risk of the goverment confiscating your miners (like in Venezuela,for example)
4. if you are planning to mine at home,make sure you ready for the noise your miners will produce
some of them sound like a mini turbine and it is prety much impossible to live in one room with 3-4 of them
5. mining time is your money and any malfunctions cut into your profit and delay ROI even more
so buy your equipment from authorised shops to be able to send them back for repairs,or pay less for a second hand miner and be prepared for it to die
at any moment as the newest miners are very unstable in this regard,people who mine say there is a 20-40% chance of your equipment to break during the warranty period
i.e. every third of your miners could break
6. business plan and the exit strategy,know where to sell your equipment and how to calculate your gains and expenses
know when to exit if the difficulty is too high,your miners become less efficient or outdated and the bitcoin price is not moving up as fast as you planned
hope this helps,but my advice is:buy bitcoins today and sit on them
you should be much better off than investing into mining
