100BTC in 5 years is really posible. You need to have a good plan to have it. it depends on you how you want have it.put full of effort and you can make things possible. It's your dreams you need to take an action don't waste too much time. Doing something not important just focus on your goal.
Assuming you can make atleast 1 bitcoin a month, in 5 years you can only make 60 btc, and if you push it harder, you gotta sacrifice some of your personal things to avoid spending. Not to mention that if there is a price increase, and the earning when the price increase decrease too. Lucky if you are single and if you have no other things to do in life, then you could really make it with full focus.
And the question is, is earning 1 bitcoin a month possible? We are not talking about our day job but bitcoin as it is. Since Day Job wage is in their local currency. Unless you learned how to trade or got a good project that pay more than 1.5 BTC per month, the dream of having 100 BTC in 5 year time is next to impossible.