How should I evaluate my startup?(specific question) If I have a startup that produces a product that I estimate to sell 100/per month, with 50%profit, and $200 is the customer price of each product, How can I evaluate this business to find investors?
First of all, valuation, especially for startups, is a topic without much consensus on the single way to do it. You can take several approaches, such as DCF, multiplayer, prepetuity and EVA (or residual income).

One frequently used way to make a valuation of projects and businesses is to use the Discounted Cash-Flow model, where you estimate the profits and losses for each year, including the financing and the depreciation you would have from the initial investments. This will give you the expected net result of the project, discounted to today (the net present value).

As some startups have difficulties in projecting costs and revenues, alternatives such as the multiplier method are used by some entrepreneurs &amp; investors. I do not consider this method very accurate, as it is easily manipulated by the choice of multiplayer.

Go beyond the numbers

If you're looking for investors to fund your large initial investment, you usually need to provide proof that you can actually sell to your customers. If you could get customers to sign already a future commitment to buy this would help investors trust you and fund you.

You can also try to resort to debt or public grants for starting a business, or try to anticipate some sales revenue to finance your startup. Get legal advice  before signing with an investor, this is critical to ensure you still get a fair share of the deal.