Yes you can make good profit, but if you have a portion of income per week like $40 per week you can invest $10 in bitcoins. This will reduce your financial risk which is much more bearable than months.
It doesn't necessary matter when and how much of Bitcoin one is buying, either weekly or monthly what is must important is that you are buying Bitcoin based on and within your financial discretion, there are those that receive money on monthly basis and of course they may find much of the comfortable buying Bitcoin at the end of the month and this doesn't make them less in their Bitcoin accumulation journey especially if they can become consistent, understanding your income flow and the best way it can be maximize by good funds allocations on your living expenses, investments and a provisional emergency funds which is also very important.