Google Autocomplete – go to google.com, start typing a phrase and look at the dropdown autocomplete results. You can use the underscore character “_” to have Google fill-in-the-blank. Just make sure the last character you type is an underscore. Try using plurals and change the word ordering to see different results. This is how I find 90% of my keywords.
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.