You can always approach investors, but keep in mind that the less you have on paper and planned, the less equity you bring to the table and the more of the business you'll probably have to give up in order to get monies.
If you want successful investment, you might consider a well thought out business plan, which includes things like income projections, costs, current valuation of the business, future valuation of the business, how soon you'll reach profitability, and what you'll do with the monies.
Most of the time, investors are very keen to invest in something that gives them a return, and the less information and market research you have to show this, the more of the business you'll probably have to give up in order to get fewer funds. Showing an investor how a $50,000 investment will net them $100,000 in 3 years, and another $20,000 each year after that is much better than just saying "we have an idea, we think it will make money, but we have no idea when, how much, or for how long"
When pitching, do make sure you're honest, and simply lay out the expected costs, potential roadblocks, any competition, and how you plan to differentiate yourself.
Hope this helps! Let me know if this isn't clear.
Also keep in mind that businesses (especially Corporations) work on a valuation system, so the stock you own is proportional to the value of your contribution, meaning that if you can value your contribution as 100 hours at $50 per hour, your contribution is $5,000. Asking an investor to add $10,000 would mean your contribution is work 33% of the business. If you want to not base ownership on contribution, you might consider an LLC, which is much cleaner about how to distribute funds, regardless of contribution. Just more food for thought.