It is true that in the past majority of working people had only one profession. Nevertheless, at the present time, more and more people have more than one profession at the same time.
To commence with the negative side, there are two disadvantages. Firstly, it would be difficult to people who have a more than one job, for instance, they will not have a time for their family or for themselves. They will work all days from morning to evening. Secondly, usually a large number of people who work a lot, they have not enough time for traveling and see the world.
Turning to the positive side, there are three advantages. First and foremost, people who have more than one job, usually they earn a lot of money because the state pay twice as much for their hard working. Furthermore, working in a many job at the same time very helpful for people especially for men who have to feed their family and children. It is a good chance to earn money. Last but not least, majority of people who have a good potential in many profession, they have a chance to show it and work more than one job at the same time.
In conclusion, even though the trend has its demerits, merits are bound to exceed.