so what's the minimal amount to invest and get about 5$ per day ?!
You are expecting to get 10% return per day which would require you to make a huge investment. Make sure you don't use sites like BTCjam for giving loans and and investing on projects. I don't trust them at all. Your best bet is to make investments in casino like around 4-7btc to get that much profit which again depends on how lucky the house is.