Betty-

The valuation for an early stage company is entirely made up.

A business analyst / lawyer / accountant can come up with a nice formula that will talk about your assets , monthly revenue , expenses , etc.

But, honestly, anyone with a two braincells and excel spreadsheet can do that.

I often get asked to look over numbers for investors and corps. I'd say that 99% of the time, the numbers and business plans are completely wrong and way off the mark. Founders make really dumb assumptions. Business Analysts / accountants/ etc often don't know what the heck they're talking about -- they don't understand the industry ( if they did, they'd be in it ). Advertising revenue is often either grossly inflated or severely undervalued; same with licensing and PS. All the good investors know that - they're wondering if there's any real value in there; but it largely doesn't affect their decision. They're more interested in the people and the product.

Your best bet as an early stage company is to push for Seed Round financing under the terms of a Convertible Note, where your company remains unvalued until a future round of financing. You get some cash, build and market the app, and hopefully have enough traction to raise a Series A or exit, at which point the early investors get to exchange the note for stock at the current valuation ( they get the benefit of compounded interest and a discount on shares bought, which can often mean 35% more buying power ).

Unless you generated a lot of money for an investment firm in the past and they're eager to re-invest with you, you will have an incredibly bad experience trying to value and raise investment for an unbuilt mobile app. This will largely be because you'll be busy marketing against investors who typically don't do risky tech investments and are coming at things from the standard 'east coast' private equity investment mentality of 'what's in it for me?'.

IMHO, at the stage you're in, you should really to focus your energy on people/groups who are familiar with this space and say things like 'I like you, I like this idea, I want this to happen, I think you can do it, I'm willing to invest X/Y/Z and introduce you to these 10 people'. It might also make sense for you to try and get into an incubator/accelerator program. At an early stage, going after the typical numbers driven investor types tends to be lot harder to successfully pull of, it takes a lot of energy , leads to fewer connections , and leaves you with less time to focus on your product, customers and team.

If you're serious about going after this investor , then do what most other people do -- start with the end numbers that will impress him, then back into them by devising various product lines.