Yes is the short answer. Any time you are planing on generating money, you should have a plan. No plan means no real focus. There may be some 1/1000 percent of a chance you will succeed, but I haven't met them yet. If you have already started and have generated an income, record how. Doing so will give you material for use in expanding your business faster.
The amount of money you can make can depend greatly of you budget. If you have a small budget and you don´t have a lot of money, then you have to start with free marketing methods like article writing, blogging, forum marketing and such. It takes a lot more effort ant time to have success with these methods. But they are very effective if you keep writing articles and participate in forums. You can make $100 a day within just a few months just with article marketing.