I think if you have the money to invest in mining wither its hardware or cloud-based it makes sense, but $4000-$6000 isn't just sitting on everyone's shelf or in their bank account like that. Those on a smaller budget might want to start with a few alt-coins, $20 on a $0.01 coin will get them 2000 coins in which their money will double every $0.01 it increases. But when dealing with alt coins there are key factors to realize such as the satoshi rate and the actual technology and development of the coin. In other words, if you are going to start small do some research and find creditable crypto news sources on why the coin will rise or never get off the ground. Only other good thing about investing that low is you can only go up!