I think that when Bitcoin reach the cost of 7K you can buy.
This time, the very now, it is a great opportunity for everyone to invest in bitcoin because the prices are low now. And talking about the profit it can give you if you invest in it, well it is very obvious from the previous statistics of biotin that its prices were leading the board, among all the other crytocurriencies. A rule of thumb for me is to buy when the market is low and cash in when they're high