I would absolutely buy a tandem. If you don't , you will be limited to the work you can do. I will also say the majority of work will require a tandem, so that part should not even be questionable.
I have driven for 19 years, and I just bought my own truck a year ago. I have leased on to a company. They have given me steady work, enough to survive. I do whatever I want on the side. I use their authority. I must give them 25% of whatever I make. Not to bad, because insurance is real cheap, and they handle fuel tax and permits. It has been working out nice for me. I have been learning a lot from doing this. If I go out I my own completely, I have learned much about doing it alone. Still a lot more to learn.
Point is, it is much more advisible to lease on to someone before going completely out on your own. That is my opinion from my experience.
Hope this helps, and good luck.